Obeche is a West African wood used to make a variey of veneers. It is heavier than balsa, but harder. It is commonly found as sheeting on foam wings in European kits like Graupners, 1mm thick. It makes a very decent, if a little heavy wing skin. Not directly connected, but did find this interesting link on covering obeche skinned wings:
http://www.scalesoaring.net/ultracot.html