I think the register book is "a few dollars "....$5-$10
I don't know about gold and it depends if stones are real or not. In our company's service award program a diamond signifies 20 years and the other stones are probably 5 year stones. My guess it is a 30'year ring. The logo is the 60s or later. Check ebay for Texaco rings and a jeweler for scrap value. A Texaco collector would probably pay more. How much. No clue. I collect Texaco. It haven't ventured into the service pins or rings. Others may chime in.

Looking for Texaco and Power Gasoline items