Diagnostic Controls & Presets Only 2 Known In Existence • $456,000 Rarity
Diagnostic Forensic Readings
Forensic Attribution Diagnostic
Real-time metallurgical and die variety cross-examination verified against certified populations.
Technical Breakdown: Physics, Metallurgy & Die Diagnostics
Proof Mirror Die vs Business Die Physics
Proof coin dies undergo diamond-paste micro-lapping to eliminate all microscopic lathe lines, followed by heavy chemical acid-pickling of recessed devices to create the frost layer:
Under 40× stereomicroscopy, an authentic 1975 'No S' proof displays deep planar optical reflection with razor-sharp 90° square wire rims formed by hydraulic dual-action high-tonnage strikes (110 tons vs 45 tons for circulation strikes).
San Francisco Working Hub Attribution
Prior to 1985, mintmarks were hand-punched into individual working dies at the Philadelphia Mint before shipment to branch mints. Exactly one obverse proof die for 1975 Roosevelt Dimes escaped the mintmark punch:
Every 1975 dime from pocket change without an 'S' was made in Philadelphia (585,673,900 minted). Only coins sealed inside original 1975 Proof Sets with mirror fields can qualify for authentication.
Documented Benchmark Auction Records
Heritage Auctions / GreatCollections Archive. One of only two known specimens discovered by an Ohio family who purchased five 1975 Proof Sets from the U.S. Mint for $7 each.
Stack's Bowers Galleries Rarities Sale. Certified PCGS PR-66. Discovered in 1977 by a California collector and confirmed by the U.S. Mint as an authentic un-mintmarked proof error.
Regular circulation issue with Full Bands. Common in pocket change with over 585 million minted; value in average circulated condition is exactly face value (10 cents).
Frequently Asked Questions
Why is the 1975 'No S' Proof Dime worth over $450,000?
Only two specimens are known to exist in the entire world. In 1975, the San Francisco Mint struck 2.8 million proof sets, but exactly one obverse proof die was accidentally put into production without receiving the hand-punched 'S' mintmark.
I found a 1975 dime with no mintmark in my pocket change. Is it the $450,000 coin?
Almost certainly no. The Philadelphia Mint struck 585,673,900 dimes in 1975, none of which had a mintmark. Business strikes have satin luster and rounded rims, whereas the ultra-rare coin is a proof with mirrored fields sealed in an original proof set.
How can I prove my 1975 dime is a proof and not a regular coin?
Proof coins have mirror-like reflective fields, frosted cameo devices, square 90-degree wire rims, and were struck at least twice under immense hydraulic pressure on specially polished planchets.
Can someone fake the 1975 'No S' Proof Dime?
Yes. Counterfeiters often take an ordinary 1975-S proof dime and mechanically buff or grind away the 'S' mintmark. Under 40x magnification, this leaves telltale tooling scratches, metal depression, and destroyed field planarity.
Where were the two known 1975 'No S' Proof Dimes discovered?
Both were discovered in original six-coin 1975 U.S. Proof Sets purchased directly from the U.S. Mint. One set was purchased by a California collector in 1977, and the second was bought by an Ohio farm family in 1978.
Did the U.S. Mint make other 'No S' proof error coins?
Yes. The U.S. Mint also released the 1968 'No S' Dime, 1970 'No S' Dime, 1971 'No S' Nickel, 1983 'No S' Dime, and 1990 'No S' Lincoln Cent.
How should I submit a suspected 1975 'No S' dime for authentication?
Submit it directly to PCGS or NGC in its original government holder without opening or touching the surfaces. Third-party grading certification is required before any auction house will accept it.