Welcome! Your coin looks authentic with spot-on Dahlonega striking characteristics on the "U" of UNITED, the "5" in the date, and obverse dentil weakness from 7-8 o'clock. The time it obviously spent in a piece of jewelry also attributed to the overall "mushy" look. Unfortunately, as an ex-jewelry piece, its value is significantly reduced, probably by half of what a fully original piece of the same grade would bring. Still a rare coin and probably has a great story behind it as to how it made it over to Europe.