The flatter top profile to the bell does suggest 50s. I'll have to consult my notes to see which ones. *edit* no joy on the flatter top profile of the bell because my note says it was the Hollow Block which had more of those, and yours is clearly no Hollow Block. If you don't know what that means you need to read that stuff. It is possible (but not evidence based) that it might increase the probability that yours is a Large Stamp -- the variant without the three dots and not the Hollow Block. But to demonstrate that to us, you need to measure the height and it must be 1.75" or more. That's in my writeup as well.
In the second photo, yes that's a more "modern" bell shape. What you describe as machining visible on the bell is due to lathe chatter (from what I can see of it) and this is more common in pre 1960s cymbals but doesn't go away entirely. The shift to having more or less lathe chatter (both in the proportion of cymbals showing it, and the degree of chatter) is gradual rather than some sudden change.