I am a collector of antique photography and gutta percha cases. One of the more interesting gutta perchas in my collection is one that dealers call, for obvious reasons, an Oreo. When this Oreo is taken apart (you like to take them apart, don't you?), it reveals a locket-like tintype.
Gutta percha is a natural rubber from the Malaysian gutta percha plant, seen below, and that natural rubber was used for a number of applications. According to the George Eastman House, however, the gutta percha case was nothing of the sort. It was actually an early shellac-based plastic dating to 1854.