Well, you can look all that stuff up but Barr notes are signed Barr -- very short time at the job and therefore a little scarce, and Star notes have an * in the serial number.
I doubt that a silver certificate was circulating all these decades, so I think someboy cleaned out a drawer for an elderly relative and didn't know why the bills were saved. Which is a shame, but a bit of luck for your son! Yea! At least it was found by somebody who cares and now it will have a good home.