I believe 2577-2* cases have this case back style. Investigation here:
https://omegaforums.net/threads/seamaster-bumper-dial-fonts.78424/

Also, I haven’t investigated this throughly but it seems to me these have a slightly different lug design as well - I notice it from the side.

 

I believe there is a third version which has a Seamaster engraving on the back. Can't remember if it has the step or if it is smooth like this one.

The 36.5mm bumpers come with different casebacks too.

 

And I'd like to comment that I called dirty not damaged

 

Amazing outcome. Love this post start to finish. Did it come with paperwork or was that just for the photo shoot?

 

Box and manual included

 

Nice purchase. You rolled the dice and took the chance on it!! Congrats.