Help needed with tri color Omega

Hello Omega experts

I got this at an estate sale over the weekend. I'm hoping you can provide some details as to age, rarity, caliber, etc. In combing the Net, I could only find another example, and that was a Seamaster. I would have liked to have opened the case, but my tool would work with the spacing of the 4 notches, so if there is another tool I can use, pointing me in that direction would be great as well.

Thanks in advance for your time

James