My grandfather built a mandolin for my mother, could easily be 75 years ago, and as a skilled carpenter and clarinet player (and a father of five with a small budget) he had to improvise. So instead of a bone nut, it has a little L-shaped metal plate, with slots for the strings, which is suspended by two screws (originally, one is now missing) and is therefore a height-adjustable nut.
The mandolin has a nice inlay of a butterfly in a flamed Afrormosia top veneer. (That is an actual wood species, I looked it up as I wrongfully doubted my mom's memory!) The body is plywood. but the back and sides have a beautiful walnut veneer, and the neck looks like it may be solid mahogany. Too bad the top looks so cracked, and the tuners are in bad shape, I don't dare to string it up completely.