(1964-65) Blank Pattern - RB-5365, INCO

Coin Details

Description

Experimental quarter-sized blank RB-5365 from the INCO silver replacement program, one of the final entries in the main RB-53xx composition group. This blank documents a composition near the end of the intensive parameter study that INCO conducted for the quarter-denomination planchet. Each blank in the series was accompanied by detailed technical documentation recording the exact alloy composition, the rolling and annealing parameters used in planchet preparation, and the measured physical and electromagnetic properties of the finished blank. This documentation, combined with the physical specimens themselves, formed the evidentiary package that INCO presented to the Treasury for evaluation. The selection of the final production alloy — a copper core with outer layers of 75% copper and 25% nickel — emerged from this systematic process, and blanks like RB-5365 represent individual steps along the path to that decision. The composition ultimately chosen proved remarkably successful, remaining in use for American dimes and quarters from 1965 to the present day without significant modification.

Rarity Notes

R-7 to R-8. Very rare experimental specimen from the later stages of INCO's quarter-denomination alloy evaluation.

Cross References

RB-5365 (Robinson-Breen catalog). INCO experimental blank planchet series, quarter-sized, 1964-65.