(1965) Quarter Pattern - RB-4125, INCO

Coin Details

Description

INCO experimental clad quarter RB-4125 from the 1965 second-phase testing series. This alloy variant is part of the continuous refinement process that ultimately produced the copper-nickel clad composition used for American quarters from 1965 onward. The testing methodology employed by INCO was rigorous: each experimental blank was prepared to precise specifications, struck on official U.S. Mint dies at the Medallic Art Company, and then subjected to a battery of physical and electromagnetic tests. Conductivity measurements were particularly critical, as the vending machine industry had established narrow tolerance bands within which a coin's electromagnetic signature had to fall to be accepted. INCO's engineers discovered that by adjusting the thickness ratio between the cladding layers and the core, they could fine-tune the overall conductivity of the composite planchet without changing the alloy formulations themselves. This insight proved crucial in achieving the final production specification. RB-4125 documents one step in this iterative optimization, its specific combination of layer thicknesses and alloy ratios representing a distinct data point in INCO's comprehensive testing matrix for the quarter denomination.

Rarity Notes

R-7 to R-8. Very few specimens known outside specialized collections. These experimental pieces are primarily of interest to pattern specialists and students of modern coinage technology.

Cross References

Research Blank RB-4125 (Gould/INCO experimental series)