IMO anything that can be found inside of the memorial building would be so small it would not be worth keeping. The only thing I can think of that is any good at all that I have seen or heard of would be the a couple letters of LIBERTY sometimes get in there from die clashes but still only worth a couple dollars.
Extra legs and knees are doubled dies found pretty much exclusively on coins struck during the single-squeeze hubbing era, or coins struck in the mid 1990s and on.
