I don't know. And I have asked smarter people than me. There is no reference stamped on the inside caseback, not even an Omega serial number. The 5-digit number on the inside caseback I am told is a supplier serial number.
Haven't worn in ages. Been wearing 31-35 mm thin manual for the most part. Getting wrist prepared for incoming Scurfa Bell Diver. Seiko lume great.
For those of you who don't know of Wegman's, you are now informed that it is THE best grocery store on the planet. Wore my grandfather's Connie for some late night shopping