Vintage seamaster 300's are a minefield, there are more fakes around than genuine ones, here's a thread from 2015, same caseback markings as the one you have:
www.watchuseek.com
How much did you pay for it? I've seen Genuine "T dial" military watches selling for up to $100,000.
www.chrono24.co.uk
A typical fake seamaster 300 military big triangle from...
Don't miss this one and the beautifull story from the seller: RARE Omega Seamaster 300 T Automatic Watch 1967 | eBay
www.watchuseek.com
How much did you pay for it? I've seen Genuine "T dial" military watches selling for up to $100,000.
Omega Seamaster 300 T Dial Military Issue Mint (all original) for £90,000 for sale from a Trusted Seller on Chrono24
Omega Seamaster 300 Listing: £90,000 Omega Seamaster 300 T Dial Military Issue Mint (all original), Reference number 165.024; Steel; Automatic; Condition Very good; Year 1967; Watch with original
www.chrono24.co.uk
