(1965) Dime Pattern - RB-4020, INCO

Coin Details

Description

An INCO experimental clad dime from the 1965 second-phase testing program, cataloged as RB-4020. The gap in numbering from RB-4005 to RB-4020 indicates that intermediate compositions (RB-4010 and RB-4015) were either tested as unstruck blanks only, produced in quantities too small to catalog, or evaluated through laboratory analysis rather than actual die striking. Each variant in the RB-4000 series tested a different combination of metals in the clad sandwich structure, which consists of outer cladding layers bonded to an inner core. The fundamental challenge facing INCO's engineers was producing an alloy that satisfied multiple competing requirements simultaneously: the coin had to match the electromagnetic signature of silver coinage closely enough to fool millions of existing vending machines, it had to resist wear and corrosion under decades of circulation, and it had to be economically viable to produce at scale. The 1965 pieces built upon lessons learned from the extensive 1964 testing program, which had used RB-1000 through RB-2000 series numbers for quarter and dime experiments respectively. RB-4020 represents a later iteration in this refinement process, struck on Roosevelt dime dies at the Medallic Art Company facility.

Rarity Notes

R-7 to R-8. Extremely rare. The skip in catalog numbers from RB-4005 to RB-4020 indicates this composition was part of a secondary testing sequence that produced fewer specimens overall.

Cross References

Research Blank RB-4020 (Gould/INCO experimental series)