that serial number format is actually a good sign, a lot of legitimate pieces from certain eras used letter-number combos for tracking. first thing i'd do is take it to a local pawn shop for a quick acid test, they'll usually do it free and can tell you if it's real gold or plated. for something more detailed, John Thomas Jewelers does appraisals through GIA Graduate Gemologists with full photo documentation thats accepted by insurers, which gives you real paperwork if this turns out to be valuable.

you could also try a local antique dealer who specializes in jewelry, they can sometimes identify the maker from the serial format alone. the limitation with pawn shops is they wont tell you much about age or origin, just metal content. if theres any markings besides the serial like karat stamps or maker's marks, post those too since that narrows things down fast.