(1964-65) Blank Pattern - RB-5420, INCO

Coin Details

Description

Quarter-sized experimental blank RB-5420, the final documented entry in the RB-5xxx series of INCO experimental blank planchets. As the terminal catalog number in the quarter-sized blank program, RB-5420 marks the end of one major segment of INCO's experimental output, which would continue in the RB-6xxx series with blanks of different specifications. The completion of the RB-5xxx series represented the conclusion of a comprehensive survey of quarter-sized blank compositions, providing the Treasury with an extensive library of candidate alloys from which to select a production formulation. The entire RB-5xxx series, from RB-5200 through RB-5420, documents the remarkable breadth of INCO's experimental effort — encompassing at least twenty-four distinct alloy compositions tested as unstruck quarter-sized blanks alone, alongside the struck-coin test series in the RB-1xxx through RB-3xxx ranges. This systematic, exhaustive approach to alloy evaluation ensured that the final production choice was based on the broadest possible foundation of empirical data, a methodology that contributed directly to the durability and success of the copper-nickel clad alloy system that has served American coinage for over sixty years.

Rarity Notes

R-7 to R-8. As the terminal entry in the RB-5xxx series, this blank may survive in especially small numbers.

Cross References

RB-5420 (Robinson-Breen catalog). INCO experimental blank planchet series, quarter-sized, 1964-65. Final entry in the RB-5xxx series.