No. Weigh it. There is a rare version of a 1964 that was not made of silver as they were still minting 1964 quarters and dimes long after 1964 while they were also minting clad coins simultaneously with the silver. Likewise, a 1965 quarter and dime that is supposed to be clad and is silver. There's no half and half. The planchet is either silver, or copper sandwiched by a nickel silver top and bottom. Nickel silver being a cupro nickel alloy.
The reason why it looks that way, is probably because of minor toning. As Michael said, 50% silver coinage was never produced.
