Just measured it. 43.8 mm the entire case, not including the vent, stem, etc. 40.4 mm the bezel only.
Don't understand the question, "mile marker".
I also have a Seiko that I bought while in Southeast Asia in 1968. It too is a diver watch, automatic. I just sent it to the local watch repair guy to have it gone through. I'll get a pic of it when I get it back.