Diagnostic Controls & Presets First Modern 'No S' Proof Rarity • $25,000 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
1968 San Francisco Proof Migration History
From 1936 through 1964, proof coinage was manufactured exclusively at the Philadelphia Mint (without mintmarks). Following the 1965-1967 Special Mint Set hiatus, proof production resumed in 1968 at San Francisco:
Mint employees preparing obverse working dies in Philadelphia omitted the 'S' mintmark on a single die shipment. An estimated 200 to 250 coins escaped the San Francisco Mint before technicians halted the press.
Field Reflectance and Optical Depth
Authentication requires calculating specular mirror reflectance vs diffuse scattering on the field above the date:
Philadelphia business strikes have diffuse cartwheel reflection under 40% due to radial metal flowlines created when striking work-hardened planchets at 140 pieces per minute.
Documented Benchmark Auction Records
Heritage Auctions CSNS Signature Sale. Superb Gem with flashing deep black-mirror fields and untouched original surfaces. One of the highest graded examples in the PCGS Population Report.
Stack's Bowers Rarities Auction. Exceptionally rare Ultra Cameo designation featuring thick frosted devices contrasting against deep obsidian fields.
Normal business strike without mintmark from the Philadelphia Mint (424 million minted). Highly common in pocket change.
Frequently Asked Questions
What makes the 1968 'No S' Proof Dime so valuable?
It is the very first modern United States proof coin ever struck without a mintmark. Proof sets moved to San Francisco in 1968, and an estimated 200–250 proof dimes were accidentally struck without the required 'S' mintmark.
How do I distinguish a 1968 'No S' proof dime from an ordinary pocket change dime?
Proof dimes feature flawless mirror-reflective fields, razor-sharp square wire rims, and frosted reliefs. Pocket change dimes made in Philadelphia also lack a mintmark, but they feature dull, satin, cartwheel luster and rounded beveled rims.
How many 1968 'No S' proof dimes are known today?
Numismatic experts estimate between 200 and 250 coins exist today across PCGS and NGC population reports. Most were found inside original 1968 U.S. Proof Sets.
What is the current market value of an authentic 1968 'No S' proof dime?
Values range from approximately $15,000 for a PR-65 specimen up to $35,000+ for PR-68 Cameo or Deep Cameo condition.
Can a normal 1968-S proof dime be altered into a No S dime?
Yes, unethical individuals sometimes abrade or grind off the 'S' mintmark. Professional grading services use optical magnification to detect localized polishing concavities and telltale disrupted field flowlines.
Did the 1968 Proof Set have other 'No S' denominations?
No. Only the Roosevelt Dime had an un-mintmarked obverse die in 1968. The Lincoln Cent, Jefferson Nickel, Washington Quarter, and Kennedy Half all properly carried the 'S' mintmark.
How should I store or preserve a 1968 'No S' proof dime?
Never remove it from its original hard plastic mint holder unless sending it directly to PCGS or NGC for grading. Fingerprints or air exposure will cause catastrophic permanent haze on proof mirrors.