Take a closer look at the TRUST on the obverse, paying close attention to the serif on the letter U. If you happen to have the DDO variety, that's one of easiest ways to identify it. https://www.pcgs.com/coinfacts/coin/1964-50c-ddo-fs-102/147846 In terms of any DDR attribution, I'm not familiar with what to look for.
There is more than a little truth to @paddyman98 's jest. Manufacturing coins is a giant industrial process on a scale that is hard to imagine. "In 2023, the U.S. Mint produced over 7.4 billion coins in the first half of the year." Things go wrong. Things aren't 100% perfect. If you look with enough magnification, you will always find SOMETHING. BUT - the harder you have to look, the less valuable something is.
