Archaeological discoveries

What are the rare silver quarters from 1942 to 1964?

The rare silver quarters for the said dates are the "Mercury Head Quarters". The US started minting these dimes from 1916 to 1945 featuring the design from Adolph Weinman. However since this quarter contains silver, the US Treasury has recalled most of this and melted many due to a shortage of silver that happened after World War II and rising silver prices in 1964-1980. Hence, many were melted with only the rare ones surviving that was not recovered by the Government for the reasons above.