Sterling Silver Carved Celluloid order & Enamel Rose Brooch, Germany

This beautiful vintage brooch is stamped Sterling on the back of the stem, and Germany, along with a hallmark that I don't recognize, behind the flower. The rose is made of carved celluloid, and the stem and rose bud are enameled sterling silver with tiny marcasites. One of the marcasites on order the rose bud is missing.

It looks like the enamel on part of the stem might be missing, although I can't tell for sure if it was made that way. The sterling silver on the back shows patina and surface wear due to its age.