As a result, some of the rarer dates like 1908 S and 1909 O come so weak that mintmarks are difficult to read with certainty, and occasionally the ungodly either affix an O to a genuine Philadelphia coin or alter 1909 D to simulate the rarer mint-mark.
A consequence of a different kind is the 1916 without mint-mark S. Though the Philadelphia Mint issued no half eagles in 1916, at least two survivors lack the mintmark. These are generally thought to be 1916 S's weakly struck so that S does not show. The only one I have examined is strong enough to make that conclusion dubious. Alternative possibilities include foreign matter in the die clogging the mintmark, lapping to remove clash marks, and inadvertent omission of mintmark. As neither specimen reported is uncirculated, the question remains undecidable.

Aside from this var., the rarest Pratt half eagles in mint state are 1909 O, 1915 S, 1911 D, and most other S-Mint issues. In other grades, 1929 is unquestionably rarest. It remained unrecognized until March 1944, when a specimen estimated at a routine $25 at auction brought nine times that figure. During ensuing decades, at least 60 specimens (mostly mint state with varying amounts of bag marks) were dispersed from original rolls; a fourth roll of 20 remained in private hands in 1978. Dispersal has been slow to avoid depressing the market.
Proofs 1908-15 are much rarer than those of the preceding decade, rarer than their reported mintages suggest. Doubtless heirs mistakenly spent some, and turned in others during the Great Recall of 1934. Reportedly, many of the [75P] of 1915, with some unsold 1914's, went to the Mint's melting pots in Jan. 1917. These proofs use several variants of the matte, sandblast, and satin finishes. The list herein (as in Breen {1977}) is doubtless incomplete, but any authentic proof of an unlisted finish will be an extreme rarity. Fraud artists have simulated proofs by sandblasting business strikes; but the real proofs have much more sharpness of detail (especially on feathers). Edges are much sharper than on business strikes. Some of these fraudulently altered coins aroused suspicion because the sandblast finish covered nicks and scratches. Authentication is recommended.
The Coinage Act of July 23, 1965 (PL 89-81), Sect. 392, has apparently restored legal-tender status to half eagles.

PRATT'S INDIAN HEAD DESIGN
Designer, Bela Lyon Pratt. Engraver, Charles E. Barber, after Pratt. Mints, Philadelphia (no mintmark), New Orleans (mintmark O), San Francisco (S), Denver (D). Mintmarks 1. of arrowheads. Physical Specifications, Authorizing Acts, as before.
Grade range, VERY GOOD to UNC.; not collected below VERY FINE. FINE: Knot of hair cord visible; partial feather contours both sides; full date, letters, and stars, but no central details. VERY FINE: Over half headband details; hair-cord knot clear; partial internal details to Indian's feathers; partial details on breast and leg feathers, over half wing-feather details. EXTREMELY FINE: Isolated tiny rubbed spots only; partial mint luster. UNCIRCULATED: No trace of wear; look on cheekbone, headdress below BE, and shoulder of wing (below back of eagle's neck). NOTE: Mintmarked coins are often weak in centers and at mintmarks.