I was looking for some clarification. I recently purchased a used Seamaster 300m reference 2551.80.00. The serial number is a 49,xxx,xxx series which I believe dates it to the mid 80's. However, I don't believe that reference debuted until 1993. Am I missing something or do I possibly have a piece that is not authentic? Thank you for your help.

 

That is a mid size Bond Auto. What you are missing is that the 2551.80.00 model wasn't launched until 1994 (the quartz movement was 1993) and indeed used movements with numbers which seemed to date earlier, possibly because they had been on the shelf for a while but also because Omega doesn't always increment numbers the way you would think. Your watch is likely from 1994-6 and the number is fine.