Hi Delia,
Darn...I’ve spent hours trying to figure out that signature. Figured if it was famous you’d look at It and go..” oh, that’s a....!” Like Micheal Angelo’s perfect circle.... The closest I’ve been able to surmise, with tracings and rubbings is.... au gabbert or ow gabbert, possibly gabbeth. Best I can do and I’ve done a lot of lettering and engraving. I just did another rubbing and have studied it under heavy magnification, all to no avail.
Cheers,
John

Bingo!
I plugged "Gabbert" into one of the price databases we use and came up with Owen W. Gabbert, a California artist still alive and working (http://owengabbertdesigns.com/index.html).
He doesn't have many auction records (Mearto gives auction records rather than retail prices). One 19-inch diameter mixed glass disk that sold in 2018 for about $200 and a set of two larger stained glass window panels that were offered in 2012 at $1,000-1,500 but which did not sell.
Taking all that into consideration, if you were to sell this at auction, this is most likely:
Owen Gabbert (California, 20th/21st Century)
Untitled abstract map/globe
three-dimensional stained glass in a copper frame
signed below OW Gabbert
30 inches diameter
$400-600*
*represents a fair-market value for auction purposes; retail or asking price may vary.

Excellent work....thank you.
Cheers, John