These would likely be mislabeled gutta-percha.
Few materials are as misunderstood, or misidentified as often, as gutta-percha.
Most likely the case actually is composition, a mixture of shellac and sawdust perfected in the mid-19th century. Check out the blackish rubbery brooch or locket, and it, too, will probably be labeled gutta-percha. Most likely it's Vulcanite, the creation of noble American inventor Charles Goodyear. Those really are gutta-percha. Christie Romero can get pretty worked up about the subject.