Kyle, sorry I didn't respond yesterday. I'm no expert, and it's too late for this gun now, but here's some info.
The gun pictured has an internal extractor, "thumb print" slide and ring hammer. Those are your first three dating characteristics. I think they stopped using the internal extractor in the early 1960s. I think the thumb print slide was only used in the 1940s-ish. The ring hammer is the original design feature; it changed to the spur hammer in the early 1970s-ish. I don't know what's up with the "257" on the right side. May be a rack number. Your pictures show a gun that is in very good condition.
Hi-Powers are, at least for the moment, selling at a premium because a) FN stopped making new ones and b) the pandemic.
This site is a good place for info on a gun like that one:
https://highpowercollectors.proboard...threads/recent
Cheers.