Finely detailed vintage 800 cameo brooch/pendant & sterling chain

Both the carving and the silver work on this oval shell cameo, measuring just over 3/4 inch, are finely executed. Thie piece can be worn either as a brooch or a pendant, thanks to its fold-down bail. The cameo is marked 800 on the bottom of the back of the frame. There may also be a maker's mark, but I can't be certain. There is a name signed in script on the back of the shell, which is an element I haven't seen before. The 15-inch chain is marked 925 Italy (and also has what I think is a maker's mark, but I can't decipher it, either). In very good condition, with some patina and a bit of tarnish on the inside back rim of the frame, which can't be seen when wearing.