Sometimes when a Punch in Blanking Press becomes just a little worn it can fold the clad layer over the sides and hide the copper core giving the coin the appearence of a silver coin...
They did but they continued making 1964 coins well into 1966 with clad production and 1964 (dated and in a 90% silver content) production occurring simultaneously. They continued making 1964 dated coins through an act of Congress to alleviate coin shortages and hoarding once the new clad coins were released. There is a very real possibility that a 1966 dated quarter could be made on a silver planchet but very unlikely and quite rare if one is found . My suggestion is to weigh the coin first against a clad quarter. Use a Popsicle stick as a balance and compare against a clad and a silver quarter. If silver, the coin needs to be authenticated, but those coins are incredibly rare and command a very large premuim. good luck!
Actuially they stoped making quarters with 90% silver in 1964 but the 1965-1969 quarters are about 30% silver. Now if you had a 1964 quarter it would be worth $4.05. I'm not sure how much the 66 quarter is worth in silver yet
Where do you get your information from on a 30% silver quarter? Go pick up a Redbook and read the information on the Washington quarter from that. They were copper-nickle clad from 65 on for business strikes, there is no such thing as a 30% silver anything.
I think every once in awhile, a new member just likes to add a silly comment onto the end of a 16 month old thread.