Cool! This is a fragment of fossilized tusk from a stegadon, an extinct relative of elephants, mammoths and mastodons. Ivory tusks grow in layers forming rings, like tree rings, with the newest ring at the centre. If you look closely you can see how the specimen is structured in layers. In the second photo you can see the growth rings. The specimen is a little shiny as it was naturally rather chalky, so I used museum consolidant resin to strengthen it.
Stegadon fossils have been found in Asia and Africa, dating from the late Miocene to the late Pleistocene (11.6 million years ago - 12,000 years ago). Most of the sub-species were larger than modern day elephants but one population on the Indonesian island of Flores became much smaller. This piece is from somewhere else on Indonesia. It is mounted on a wooden base and will work well in 1:12 scale.
3/4 inch (1.9 cm) wide, 9/16 inch (1.4 cm) deep and 9/16 inch (1.4 cm) tall.