Diagnostic Controls & Presets Frontier US Assay Office Colossus (2.5 Troy Ounces)
Diagnostic Forensic Readings
Forensic Attribution Diagnostic
Real-time metallurgical and die variety cross-examination verified against certified populations.
Technical Breakdown: Physics, Metallurgy & Die Diagnostics
Fineness: 880 or 887 Thousandths Pure Gold
Authorized by Congress on September 30, 1850, United States Assayer Augustus Humbert partnered with private mint Moffat & Co. to strike massive octagonal ingots to stabilize the chaotic California Gold Rush economy.
Anti-Clipping Security: Full-field geometric engraving
To prevent corrupt gold speculators from chiseling off gold corners or shaving edges, the reverse was decorated with an intricate rose engine guilloché pattern that would instantly reveal any physical tampering.
Melted: Over 98% melted when SF Mint opened in 1854
When the official San Francisco Mint opened in 1854, commercial banks were forbidden from accepting Humbert slugs. Tens of thousands were melted into regular federal $20 Double Eagles, making survivors premier trophies.
Documented Benchmark Auction Records
Tied for finest certified octagonal slug; shimmering golden-olive luster with completely intact lettered edge inscriptions.
Ex-Eliasberg. Superb eye appeal with needle-sharp engine-turned rose rosettes and minimal corner contact marks.
Pioneer saloon survivor with authentic rim bruises and bold central eagle holding the US Assay Office ribbon.
Frequently Asked Questions
What is an 1851 Augustus Humbert $50 'California Slug'?
The 1851 Humbert $50 slug is a massive, eight-sided octagonal gold ingot weighing approximately 2.5 troy ounces. Produced by Augustus Humbert, the appointed United States Assayer of Gold in San Francisco, it served as quasi-official federal legal tender during the height of the California Gold Rush before an official US Mint branch was established.
Why were these $50 coins made octagonal instead of round?
Because the private firm of Moffat & Co. (operating as the US Assay Office of Gold) lacked the massive mechanical presses required to strike round 2.5-ounce gold coins under high collar pressure. The octagonal shape allowed workmen to roll and trim the thick gold bars using simpler blacksmith collars while preventing them from rolling off gambling tables and merchant counters.
What does '880 THOUS' or '887 THOUS' mean on the coin?
The numbers represent the metallurgical fineness (purity) of the unrefined California placer gold. '887 THOUS' means the ingot is 88.7% pure gold (887/1000 fine), with the remaining 11.3% consisting of natural silver and trace copper directly from the Sierra Nevada riverbeds.
What is stamped on the edge of the Humbert slug?
Authentic early Humbert slugs have a lettered edge impressed before striking: 'AUGUSTUS HUMBERT UNITED STATES ASSAYER OF GOLD CALIFORNIA 1851'. Later varieties produced under the US Assay Office feature reeded edges.
Why is the reverse of the coin called 'Engine-Turned'?
The reverse features an intricate, spiraling geometric pattern known as a 'target' or 'rose lathe' design. Created by a mechanical rose engine lathe, this complex pattern made it impossible for dishonest individuals to scrape, sweat, or drill out gold from the back without immediate visual detection.
Why are genuine Humbert slugs so rare today?
In 1854, the official United States Mint at San Francisco opened its doors. The Treasury decreed that all private and assay office ingots must be deposited and melted down into standard federal $20 Double Eagles. An estimated 98% of all Humbert slugs were destroyed in the melting furnaces.
How can you tell if a Humbert $50 slug is authentic?
Key authentication checks include: (1) Exact weight between 1,310 and 1,330 grains (approx. 85.0 to 86.2 grams); (2) Archimedes specific gravity of approximately 17.0 to 17.5; (3) Sharp engine-turning lines on the reverse; (4) Proper letter punches on the edge with no casting seam along the 8 corners.