CCCP and Silver

One of my recent buys included 2 1961 CCCP coins. Numista says they are aluminum. But I swear they sound, look, and feel like silver.
Soviet Union.....CCCP!
There are either a "15" and "20" or some other small amount.
Any help from the pros?
Soviet Union.....CCCP!
There are either a "15" and "20" or some other small amount.
Any help from the pros?