Yes, but long before 1964 .... Nevada... being a silver producing state..., had mandated through legislation the use of silver dollars exclusively for use in their casinos (the last silver dollars were dated 1935). Silver Dollars had just under one ounce of .999 fine silver in them that was valued at $1.29 per ounce melt value in the early 60's when they began to disappear in huge numbers from what I recall. The law in Nevada first had to be changed in order for the Franklin Mint in Philadelphia to be allowed to supply gaming tokens for the Nevada slot machines.