Posted by John Purdy on 05/06/2023 18:24:44:
My Stuart beam is probably from the '70s or '80s ( I got it part built second, or more, hand ) and the number on the base is 80063 and on close examination with a loupe is definitely cast in not stamped. So I would assume it is a casting number.
John

The number on mine is probably she same as yours. It is quite faint on mine, so I posted what I thought it said. My base casting was a replacement that I bought from Stuart, so it is from a different vintage than my casting set, (the original was a terrible casting. The raised Stuart lettering was very defective and quite unappealing).