the font of the first S in seamaster on the first watch looks more legit to me for an early 50's watch. The lower curve on the second one looks more like 60's era.
If the second one is a 2587, the rounded S looks correct. There seem to be very little 1950's semaster with that rounded S.
Both are seen throughout the 1950s. There have been similar threads on here showing several round S examples. There is no hard and fast rule on which S is right at any given point in the '50s, in fact if anything the coat hanger is more rarely seen.
First one seems to be original…normally you don't see the concentric circles on subdials when it is redialed