I have discovered one of these as well, it's also 1965 and also magnetic.
and all the others I have seen discovered are also 1965. I wonder what took place for these to all have matching years?
I believe the theory of others that say they were a homebrew experiment or something related to that. school project, jewelry, decorative ect.
but all 1965 is interesting. If somebody did this 1965 with a roll of pennies you would think the base penny would be in better condition, but the ones I have seen are obviously circulated with the plating over top of scratches. You would think somebody would use better qaulity pennies. idk. fun find though.