I thought 1965 quarters and older were silver and I had ten of them...it turned out 9 of the quarters were 1965.... and it also turned out 1965 is not a silver quarter.... but out of my 10 one was silver.... so I would say a good estimate would be for every 9 coins you find of every type and other date, you should fine one silver... meaning 9 coins of 1965 quarter, 9 of 1965 penny, 9 of 1965 dime and