In 1968 Canada made a .500 silver quarter and one that has steel in it. The way to tell them apart is with a magnet. If it does not stick the coin is .500 silver.
Before 1967 the quarters are .800 silver. In 1967 they made a .500 and a .800 silver quarter. I don't know how to tell them apart since they say that they both have the same weight .This is from a coins mag. that has a Canadian price list.