Any idea what year range this Seamaster is? It has a winding mechanism, probably loses a minute per day. I am looking for an appropriate watch band to replace the aftermarket Speidel (his wrist was much smaller than mine)...I'm thinking beads of rice perhaps?
Surefire way of getting the date is to have the caseback opened and look for the serial number on the movement. Then check for the date by googling for Omega Serial Numbers. Such as this ...... http://chronomaddox.com/omega_serial_numbers.html
Welcome to the OF. Lovely watch That looks awfully similar to my late Grandfathers watch (caseback reference : 166 001). When I google it, it looks like yours too. Then as @waterproofpt mentioned, you need the movement number to correctly date it. According to the movement number in mine, mine is about a '63. Go to your nearest watchmaker and let them open it for you and take a pic. Edit : loses a minute a day -> most likely needs a good service.
Don't try to open the caseback (it can't be done). If you want to get all of the details from the inside take it to a competent watchmaker.
With that shaped "S" it will be earlier than 63, probably about 59-61. Nice watch, it would look great on a tan leather strap with a gold or gold-plated Omega buckle.
Unless you know when it was last serviced, while it's at the competent watchmaker, have it serviced, too.
I have one very similar but in SS You'll need one of these to open but don't bother bring it to a watchmaker. Mine is model 14775-1 circa 1960
I would not recommend using that type of crystal lift on these actually...agree best to take it to a watchmaker who has the correct tools. Cheers, Al