Big loupe and natural light, moving the watch around until it is reflected just right is my usual approach to the difficult serials. And there are still some I'm not 100% certain about all six digits, they're not stamped all that deep and 40+ years of wear and tear takes its toll on legibility.

I guess we could be looking at a 0 or a 3 on the watch, as well as a 2 - not sure how clear the serials were on the Sammy Davis Jr watch, so that could be the one that was misread too.