São Tomé and Príncipe 500-DOBRAS (KM89) Mona monkey
That's almost definitely a Mona monkey in the tree, since that is the only primate found in the area and it looks just like the (tiny) image on the coin.
This FAO coin was minted in 1997 only as part of a larger denomination coin set to deal with rampant inflation. The reverse legend is a Portuguese translation of the FAO slogan "Grow More Food" although I am not really sure what farmed food -- if any -- is depicted on the coin's reverse. What ever it is, there is a monkey about to steal it.
- Diameter: 23 mm
- Composition: Nickel-clad steel
- CAT#: KM89