A few years ago I found a abandoned kayak while out fishing in my boat. Called police dept.They said place a ad in the local newspaper for 2 weeks, (lost & found section,cost is zero for the ad ) .No one claimed it,I still have it.
I found a SS Bracelet Tag last year or so, had the guy's name engraved on it from 1953. Went to Google, Indian Steve found the guy first, or actually his children. I mailed it back to his son and daughter - their keepsake forever. There's many ways to skin a cat, and sometimes Google helps.
You could put an add out on Craigslist in the lost and found section. Don't identify the name in it. That's for the owner to tell you. No cost for that either.
I bought my Marine Corps ring at the PX. Did not register it with the mfr. If it's an older ring, the VFW might work as well.
Welcome to Treasurenet !!
If the number on the ring you refer to is the Marine's actual service number, a lot of information can be obtained.
Don........