1964 and older is 90% silver and 1965 to 1970 is 40% silver you can go to coinflation.com to see for yourself, I'm glad you have the correct information now!!! :)
If the coin is stamped S meaning san fran. mint itll be silver, usually comes from the silver proof sets. It doesnt have to be 1964 or older to be silver, thats just saying in general.