Amid much fanfare, the new United States Mint at Philadelphia was opened in a public ceremony on a summer afternoon in August 1969. The star attraction drew international attention. Rather than a Hollywood celebrity, this gala was centered on the unveiling of the new coin roller. Developed by General Motors, the machine was purported to be capable of producing 10,000 cent pieces per minute. The Director of the Mint, Eva Adams, once called it “the greatest development in the art of minting that has been made in the past 2,000 years”. Within several months, the project was scrapped and termed a failure.

The birth, short life, and death of the project form an interesting chapter in the study of mint technology. A private movie screening attended by Mint officials and GM executives is cited as the origin of the experiment. After watching the James Bond movie “Goldfinger”, a discussion of the then current coin shortage and the Mint’s difficulty with meeting production demands was met with a ‘can do’ response from the GM representatives. Based on this informal oral agreement, the challenge of inventing and producing a high-output minting machine was directed to the Manufacturing Development Staff of the General Motors Technical Center in Warren, Michigan. Within several months, in 1964, a working prototype of a “roll forming press” was churning out test pieces with the letters “GM” on one side and “MD” on the other. This trial run is represented by only two known surviving examples.

The drawing illustrates the basic concept of the coin roller. (see diagram 1) This device used three rollers to cut blanks and emboss the design. A copper alloy strip is drawn between the upper and middle roller. The upper roller contained the blanking punches while the middle roller held the obverse dies in recesses mated to these punches. Blanks were cut and loaded onto the obverse dies in a single motion. The middle roller then carried the blanks to the contact point with the lower roller, which held the reverse dies. Coining occurred as the dies slipped past each other; the middle and lower roller surfaces traveled in opposite directions. The newly minted coins were ejected from the middle roller by an eccentric cam pushing against the backs of the obverse dies. The coin roller, from its earliest conception, was designed to carry multiple interchangeable dies.

The production version of this machine had two roll forming presses working on a single five-inch wide copper alloy strip. This arrangement allowed the blanks to be cut in an offset pattern and reduced waste. The published accounts of the machine differ as to the number of dies per press, but based on the control numbers found on the most commonly encountered pattern pieces and the work to be performed, a reasonable estimate can be made. Whether detailed records of the layout and design of the machine still exist is unknown. No record of this innovative mechanism could be found in the U.S. Patent and Trademark Office. When contacted about the project, a GM representative replied, “We researched the information that you requested and have been unable to come up with an appropriate answer using the resources available.” In a Coin World article by Eric Larson published May 29, 1995, several retired Tech Center employees were interviewed regarding the project. None of the GM technicians could recall an exact number of dies, but most put the number at 72 for the system. The most likely configuration, based on the available evidence, is that the rollers were fitted with eighteen dies each, six rows set three wide. (see photo 4) One full rotation of one press would produce eighteen coins. Together, the two presses would have needed to run at about 280 rpm to yield the desired 10,000 pieces per minute. At this rate, Director Adams testified before Congress, “they come out just like water”.

Several different designs are known from dies produced by the Philadelphia Mint. The first design is the GM/MD type mentioned earlier. The second type appears to be a modification of existing cent obverse dies. These dies had the Lincoln portrait from the one cent piece with the legends and date removed and a sandblasted finish for the obverse and “MANUFACTURING DEVELOPMENT STAFF” on the reverse. Two reverse varieties are known. Examples from this issue are now listed in United States Patterns and Related Issues as Pollock 4055 and (post-publication) 4056. The third and most commonly encountered variety is called the “Lady Head” type, listed as Pollock 4060. This design features fantasy legends as well as the female portrait facing left. (see photo 1) Hand engraved die control numbers flank her image on most known examples. The letters “L”, “M”, or “R” representing the row positions left, middle, or right are found in the field to the right of the portrait. To the left of the portrait, a number 1through 6 can be found, designating which column the die was located within. Some examples also display a symbol believed to designate whether they were produced by the first or by the second press.

It has never been common practice for the U.S. Mint to supply dies to private contractors. Prior to this project, it had only been done once before, during World War II. Responding to a question posed by Larson, former U.S. Mint Chief Engraver Frank Gasparro said, “I did engrave all the dies. They were designed to strike experimental or trial coins, because it is illegal to strike official U.S. coins outside of the Mint.” In response to a follow up question, Gasparro reiterated, “All those for the GM project, I made.” In addition to the patterns, the coin roller produced Lincoln Cents. Hundreds of onlookers witnessed the machine in action at the Mint’s unveiling ceremony on August 14th. Published reports also mention a twenty-day trial run at the Philadelphia facility prior to the official opening. 119 million 1969 dated cents were minted by the roller at this time. Whether any of these coins were ever released into circulation or if they are distinguishable from the other cents produced by the Mint’s other coining presses are questions that remain unanswered to this day.

The project was terminated in December of 1969 after five years of development and placement of an order for a second machine. The coin roller apparently never worked as well as expected. Dies wore out much faster than anticipated, and the entire system had to be shut down to change single dies. Other mechanical issues were also cited, but they seem to relate to the dies and their operation. In the announcement of the project’s cancellation the Assistant Secretary of the Treasury, Eugene T. Rossides, stated “short die tool life and other mechanical problems make the coin roller uneconomical”. The machine was replaced by several knuckle joint presses fitted to strike four coins per stroke, a process developed in the Denver Mint.

What went wrong? What caused the excessive die wear and breakage? Was the project doomed to failure from the start?

The concept of a coin roller is actually centuries old. Water powered roller presses were used at a number of European mints from about 1550-1750 until the adoption of the screw press. One of the largest coins ever minted, Spain’s cincuentin (50 reals) silver piece, was produced by rolling. It is a true giant, measuring 76 millimeters in diameter. In terms of surface area, it is four times the size of a silver dollar. (see photo 3) Die wear on this type of press was not the issue that it was with the GM machine. The Renaissance and GM machine designs differ in three important respects.

Issue 1 Die faces
The machines of old used cylindrical dies with the design cut into the roller face. This meant the die face was convex. As metal passed through the rolls, only the small portion between the rolls was coined at any given moment. (see photo 2) Less area requires less force. A number of these older dies survive and show remarkable preservation on their coining surfaces. The GM press used modular die inserts and it can be deduced that they had flat surfaces. These dies were reported to be relatively thin blocks, only about .75 inches (2 cm) in thickness or roughly equal to the diameter of the cent. One of the technicians interviewed referred to a ‘knuckle’ fitted to the reverse dies to bring them into parallel register with the obverse at the moment of striking. Two convex surfaces do not need an external pivot to maintain contact through a minor arc. Two flat surfaces require it. Without such a pivot, the leading and trailing edges contact sharply, while the centers barely touch. This is not an ideal arrangement for coining. Larson spoke with another former project employee about the “Lincoln Head” dies that were used during several of the trial runs. The former Tech center employee was quoted, “We thought they were made from used Lincoln Cent dies”. Such dies have flat surfaces.

The roller presses of the European Renaissance employed another feature not found on the latter device. The dies performed additional coining on the waste portion of the strip. Small divots, or diamond shapes, are found outside the main impressions on all but the earliest roller dies. These ‘dimples’ served an important function. They dissipated the force of the press near the edges of the coining. Die pressure had to be set to raise detail through the central part of the design, but the amount of force needed to raise the outer portions of the design was considerably smaller. Again, less area requires less force. However, a careful balance between the central and outer elements of the work had to be maintained. Without this balance, a roller press will perform the function it is most often used for; it will crush and stretch metal. (see diagram 2) When the mint masters switched to the screw press in the later part of the 18th century, they did not discard their roller presses. They replaced the dies with smooth faced rollers and used the machines to produce the strips that planchets could be cut from. Roller presses are still employed in this function to this day.

Issue 2 Axis of rotation
Tech Center employees provided Larson with drawings of the basic design of the GM coin roller. Their drawings specifically illustrate the two rolls that carried the dies were set with the same axis of rotation. This meant the obverse and reverse dies would travel in opposite directions across the blank. Such an arrangement does not push work through the rolls. A number of people involved in the project repeatedly referred to concerns about elongation of the coins as an effect of the rolling process. Setting the dies to travel in opposing directions mechanically negates this effect. Unfortunately, this also produces a great deal of friction and heat. Worse still, it creates both a radial and a lateral force across the die face. The roller presses of the 1550-1750 era, as well as the blanking press on the upper half of the GM machine had their rolls set to rotate in opposite directions. Because they were set on opposite sides of the strip, their faces moved in the same direction. The blank cutting portion of the GM machine is said to have performed well. One course of action considered when the project was about to be cancelled was to convert the coin roller into a blanking press.

Issue 3 Order of operations
A major difference between the two designs is the sequence of events in the coining operation. The GM press cut its blanks and carried them to the coining chamber. While not performed by a single machine, this is the way coins have been produced for several hundred years. The older machine produced coins from metal strips instead of round blanks. This helped limit the amount of elongation of the coins, although it still was a concern. The strip acted much like a retaining collar, although some distortion was still present. The careful balancing of the coin design and the ‘dimples’ on the strip also helped limit elongation. The die force was expended to raise the metal instead of stretching it. Designs of larger diameters also frequently employed dies that were deliberately distorted in the vertical direction. Slight elongation in the horizontal dimension would yield a round coin. Running a round blank through a roller press without a retaining collar will produce an elongated oval product. Today, roller presses of this type are frequently encountered at tourist destinations. A small child turning a hard crank can easily make one of these souvenir “coins”. (see photo5) GM’s design had the obverse dies recessed in the ‘cup’ or female portion of the blanking press and this feature doubled (by design) as a retaining collar during coining. In fact, the European design is somewhat unique for producing the coin first, then cutting it free. The coins were freed of the strip by a hand-operated punch press, or for the larger issues, by giant scissors. References to coins with ‘knife-edges’ that were capable of cutting fingers can be found in writings of the period. Examples of strips with several coins together generate a great deal of interest and require some explanation to those not familiar with roller presses. (See photo 7) While this exact method is hardly suitable for a modern mint, its concept worked in its time. The issue of elongation had been largely resolved by the techniques described, but coins produced by these presses had a tendency to be curved or ‘bent’ and would not stack well. The combination of blank cutting and coining in a single machine is the greatest mechanical variant from the older design. It utilizes three rolls instead of two. By all accounts, the blanking portion of the GM press was a technological marvel.

Fatal flaws
That the project died is a historical fact. The causes of the failure have been debated repeatedly, but they all seem to focus on the dies and the way they were used in the press. There are other factors to consider as significantly contributing to a failure at the conceptual level.

The ability to use interchangeable dies has been a requirement of mechanical coining presses since their inception. The GM press was no exception. It was designed to accept dies produced by the Mint through conventional methods. However, this design fails to capitalize on the basic mechanical advantage of a roller die. The advantage is gained by coining only a small portion of the work at a given instant. Such a device would require die cylinders rather than individual flat dies. The Philadelphia Mint would have needed to use a completely different method of die production. In theory, a flat working hub could have a blank cylinder rolled across its surface a number of times until the desired number of impressions had satisfactory detail. A variation of this method has been used by the Bureau of Engraving and Printing to produce plates that print embossed currency for decades. Whether the methods of producing paper currency can be applied to coinage is a study unto itself.

It is interesting to note that during the two hundred year period that coin rollers were in use, die manufacturing was one of their major drawbacks. The die cylinders were engraved individually by hand, each impression on each die. (see photo 6) A transfer lathe capable of such work had not yet been invented. The cylinders were also not particularly well suited to reproduction by punches. This method was experimented with, but only a few small diameter issues were successfully produced. When one portion of a die wore out the entire die had to be discarded, or the coins from the ‘bad’ die had to be picked out of the mintage and re-melted. The greater ease of die production for the screw press was the main reason it won out. The practice of manufacturing dies for a screw press through the use of punches was well established at the time the last roller press was retired from coining duties around 1756. The further development of multiplying dies through use of a hub, which can be done quite effectively on a screw press, reinforced the preeminence of the machine in latter years. The screw press and the roller press were invented within a few years of each other, although the exact dates and inventors are the subject of debate. From the early decades of the 16th century, prototypes of both devices are known. Roller presses were considered ‘state of the art’ machines. The mints that employed them represent the first truly mechanized factories in human history. By contrast, the screw press was bitterly opposed by the “moneyers” that produced hammered coinage. Several nations, France in particular, briefly abandoned the screw press in favor of hammered coining to placate the concerns of its mint labor force. Some nations never used the roller press to coin. For those that did, it took two hundred years of refinements of the screw press and its applications to supplant the last roller press used for coining.

Cutting the blanks prior to minting was a departure from the historically proven method of producing coinage on a roller press. Working on pieces, rather than a strip, prevented the established methods of controlling elongation from being employed by GM’s machine. Instead, the lower rollers had to be set to work against each other. While this solved the elongation problem, as we have seen, it destroyed dies at an alarming rate. Abandoning the three roll design and cutting blanks first in favor of multi-staging these operations within a system of machines may have worked better. The GM roller was already designed as a system rather than a single unit.

Freeing the coins from the strip after minting is a challenge. In the 18th century, the roller press design was replaced both by the screw press and the basic order of minting operations still in use today. Specifically, the new process prepared planchets for coining. Blanks were cut, and then examined for defects. In the past, those of precious metal were weighed individually and adjusted or rejected. Acceptable blanks were then passed through an upsetting mill, where the rims were formed around the edge. At the completion of this step, by definition, the blanks were now planchets. The planchets were then annealed (softened by controlled heating and cooling) and cleaned prior to minting. Both roller presses skipped the planchet making steps prior to coining. Director Adams once stated that the upsetting step was performed after coining in the GM system. Without the development of a machine that could cut the coins free without damaging or significantly distorting the newly minted surfaces; the coin roller seems of little use outside of a museum environment. This was another issue that was raised in the debate to replace the roller press with the screw press in the 18th century. It is still unresolved.

Perhaps one day some industrious person or corporation will invent a coining system that marries the best features of both designs: Interchangeable die cylinders with additional coining on the strip, straightening, rotary blanking punches, and integrated upsetting. The staggered nature of the GM system was a definite advantage. It allowed for a more efficient utilization of material with a minimum of waste. A careful review of the order of operations and how it affects the finished product as well as the durability of the machine is an absolute requirement for a viable system.

In retrospect, the Mint and GM had little chance of success. They do not appear to have been cognizant of the roller presses of the past, they certainly did not attempt to incorporate their strengths. No indication of any study of the Renaissance designs is mentioned in any of the published accounts or interviews on the subject. It is understandable on the part of the General Motors executives and their Tech Center staff; their field of expertise is automotive manufacturing. A study of machines developed in the 16th century would be far outside their practical experience. But what of the Mint? The engraving department is not asked to perform historical studies of coining processes. They are asked to make tools for specific purposes. Whether Mr. Gasparro or his staff raised concerns about the nature of the dies he was directed to prepare may never be known. Even if the department had conceived of a process to produce die cylinders, they would not have been permitted to make a machine of this nature without authorization. The senior staff of the office of the Director of the Mint is charged with the duty of oversight of the nation’s coinage and coin production. It is their job to understand the minting process. A study of the history of minting technology would seem to be a prerequisite to the effective discharge of their duties. Director Eva Adams’ comments, particularly the “greatest development in the art of minting” statement, reflect a lack of historical perspective. There is a well-known admonition regarding a doom of repetition for failing to study history. The coin roller was not so fortunate, had history repeated itself, a practical machine may have emerged. This project failed to capitalize on a wealth of experience. Those who fail to study history cannot learn from it.

PCGS