When we had a brooch of this type a few years ago, I was bowled over by its massive size. Amazingly, here's one about TWICE as big and in even better shape. It measures well over 2 3/4 inches in diameter, with a dome rising more than 1 1/4 inches.
This fascinating form was developed in the Netherlands, where 18th century residents of Zeeland wore it as part of their regional costume. It retains the old T-hinge and open C clasp indicative of great age, as well as the extremely substantial pinstem we associate with Georgian times. The only departure from original condition is that the pinstem, which would have been extra-long, was at some point shortened (a good idea, since they're dangerous now that we don't wear corsets and other layers of heavy underclothing).
The metal is almost certainly 835 silver (the old Dutch sterling standard), although we haven't spotted a mark. Given the fragility of the material, it's truly remarkable that even the repousse beads show almost no dimpling.
This is a truly spectacular conversation-piece item of a sort seldom seen outside Europe and it isn't as heavy to wear as you'd think, because there's so much openwork. It reached us from the estate of a New Yorker who lived past 90. The brooch would have been antique, of course, long before she purchased or inherited it.
There's no charge for insured U.S. shipping and beautiful gift wrap is also free on request. Please e-mail to confirm availability, order or request more photos. Thanks for looking!