Sorry, thinking into this again, I take this ID back. With how limited the distributions of the other two subspecies further south in Brazil are, they're very unlikely to be imported to Indonesia in recent years (CITES data shows they mostly came from Czechia). This being the nominate subspecies seems much more likely. Sorry for the wrong impression.
Plazi mentions these descriptions:
"The nominate subspecies labiatus is mainly black with white marbling on the hindparts, with a red underside (except for the throat) and basal part of the ventral surface of the tail. The “Gray’s Red-bellied Tamarin” (S. L. rufiventer) is similar to the subspecies labiatus , but with a red, Y-shaped mark on the front of the crown and a slight silvery patch behind. In northerly populations, this red crown mark is well expressed, whereas to the south, it is barely distinguishable but has a sharply marked white spot behind. In the “Thomas’s Red-bellied Tamarin” (S. I. thomas), the throat and the upper chest are black, with the rest of the underside, including the basal part of the ventral surface of the tail, orange. The crown is black, with either a poorly developed reddish midline in front or none at all and a small pale silvery spot behind."
- Saguinus labiatus (E. Geoffroy Saint-Hilaire, 1812)
