Jim.
I looked at a bunch of these on line,..along with variants.
They all "appear" to be press fit as Bob says...I'm sure his research will verify.
Here's a shot of one with the hands removed..looks like that second hand press fits to a shaft that has a rectangular shape, and that makes sense as then it wouldn't break loose when it was reset ( flyback ).
https://picclick.com/Waltham-A-13A-1-20 ... id=1&pid=1Also..I saw another link that stated the hands came in various coatings. some luminous, some just painted white....so now, I'm not sure you actually have radium hands on this one....
Just food for thought !
Best
Randy