31 CFR § 100.12 - Exchange of fused or mixed coin.
(1) Fused coins are U.S. coins which are melted to the extent that they are bonded together.
(2) Mixed coins are U.S. coins of several alloy categories which are presented together, but are readily and clearly identifiable as U.S. coins.
(b) Fused and mixed coins. The United States Mint will not accept fused coins for redemption. The United States Mint will not accept mixed coins for redemption, except as provided for in § 100.11(d)(2).