(1964-65) Blank Pattern - RB-5380, INCO

Coin Details

Description

Experimental quarter-sized blank planchet RB-5380 from INCO's silver replacement program. This blank occupies the transition zone between the densely packed RB-53xx series and the more sparsely numbered RB-54xx group, representing a composition that may bridge two distinct alloy families. The International Nickel Company's experimental methodology involved not only testing individual compositions but also understanding the relationships between compositions — how changes in one alloying element affected multiple physical properties simultaneously. RB-5380 may represent a composition that attempted to combine advantageous properties observed in different portions of the alloy space, synthesizing lessons learned from the extensive RB-5300-5375 testing into a hybrid formulation. The blank planchet format was ideally suited for this kind of comparative metallurgical analysis, as the absence of struck design elements allowed direct, unobstructed measurement of the alloy's surface and bulk properties. These measurements, accumulated across dozens of compositions, built the comprehensive database that ultimately supported the Treasury's selection of the production alloy.

Rarity Notes

R-7 to R-8. Rare transitional composition between two experimental alloy families.

Cross References

RB-5380 (Robinson-Breen catalog). INCO experimental blank planchet series, quarter-sized, 1964-65.