that is a nice one! Well some have a makers name in the band. Some of the firms are still in business and you can trace by contacting them... Doesn't appear yours has a maker in band.. Yours does have some good honest wear to it,,maybe even combat wear[?]
- The sides of the band have a eagle with shield? IF so its a good chance its pretty old.. I'd say from Viet Nam and up most military rings have a 'Gem' on cartouche and some fancy design on band sides..
For comparison check like US eBay for American military ring, or 'ring' in Military subject area. You'll see most of the WWII rings have this eagle with shield. Don't think you'll get an exact date but when your doing the comparisons its WW2 and Korea have the 'look' of this ring.. We have some veterans here maybe they can give a better opinion..
So this link is for' US ring' in 'Militaria' and 'WWII dates':
https://www.ebay.com/sch/13977/i.html?_from=R40&_nkw=+US+ring&LH_TitleDesc=0You can try variations on your search. Vintage US ring,,,in 'All categories' etc. etc.
You might even see your ring in there somewhere! but it is a good place to start.....
Here is an example of a WWII side band.. As far as exact,,don't think you can do it without the maker. This could also probably be Korea.