(1965) Half Dollar Pattern - RB-4520, INCO

Coin Details

Description

Experimental clad half dollar RB-4520, the penultimate entry in the 1965 INCO half dollar testing series. As one of the later compositions in the RB-4500 sequence, this piece may represent a refined formulation that incorporated feedback from testing of earlier variants. The half dollar testing program, though smaller in scope than the quarter program, generated valuable comparative data that illuminated how the same clad technology scaled across different denominations. One key finding from the experimental program was that the copper-nickel clad sandwich behaved differently at different scales: the half dollar's thicker cross-section produced a proportionally smaller electromagnetic contribution from the cladding layers relative to the core, potentially requiring adjustments to maintain the same conductivity profile that worked for dimes and quarters. RB-4520 tests one such adjusted formulation, struck on Kennedy half dollar dies at the Medallic Art Company. The piece is visually indistinguishable from a standard half dollar to casual inspection, demonstrating the effectiveness of INCO's cladding technology in producing a convincing silver substitute at the largest circulating coin diameter.

Rarity Notes

R-7 to R-8. Extremely rare. Late-series half dollar experiments may survive in slightly smaller numbers than earlier entries in the sequence.

Cross References

Research Blank RB-4520 (Gould/INCO experimental series)