With some exceptions, you can go back to 1866. During WWII, some 5c coins were made out of a nickel-free alloy containing 35% silver to preserve the nickel for

With some exceptions, you can go back to 1866. During WWII, some 5c coins were made out of a nickel-free alloy containing 35% silver to preserve the nickel for war efforts. These are identifiable by a large mintmark over Monticello over the reverse. Before 1892, the nickel 5c coin was issued alongside a smaller silver "half-dime". It's likely the growth of automated coin acceptance machines (early arcade amusements, slot machines, vending machines) really locked in the base-metal coin's dominance.