Need help identifying and appraising my vintage Omega Constellation

I have an Omega Constellation Automatic chronometer certified ladies watch with gold-plated metal band. All original. It has a coin edge bezel. It shows date only (no magnified bubble), and date is hard to set. Crown has only one pull out position and to set date, you have to run hour hand back then forward til you get to the right date.
It has the observatory (?) and stars symbol on back but no serial number. I assume the serial number is inside, but the back has never been removed, so I don't know.
I purchesed it in 1974 at Anderson AFB, Guam BX. Wore it for a few years, then put it in the drawer. It's been in a drawer for the last 40 or so years. Put it on the other day and it runs fine. I don't want to sell it; I'm just curious what it's worth.

The best way to determine value is to look at the eBay sold listing.

Welcome!

Perusing through the vintage Omega database, I think yours is a ref. 568.0018 from the mid 70s with a chronometer grade 682 movement. I don't think I've seen one move for more than $500US in the past year or so, even with the bracelet.