Proof Set Question

The Bicentennial 3-pc. Silver Proof Set has three 40% Silver Proof coins: Washington quarter, JFK Half-Dollar and Eisenhower dollar,
dated "1776-1976" and with Bicentennial reverse designs.

1992 is the first year where the 'standard' Proof Sets (1¢ to 50¢ denomination set) were offered with the choice of Clad (copper-nickel)
or (90%) Silver, referring to the 10¢-to-50¢ coins in the sets.

The 1970 Proof Set has a 40% Silver Half-Dollar, the rest of the (10¢-to-50¢) coins in Proof Sets from 1970-91 are Clad (except for the
Bicentennial 3-pc. Silver Proof Set listed above).