I've had a few bits of greengage from neighbours tree pruning, so it's sort of cheating. Hard to do much with it because some heartwood is often as soft as a soft thing. As it dries out, the white bits can go a very nice rich creamy colour, the dark bits lose some contrast but don't change much. If you can get something out of it, the finish is silky-smooth. I use Danish oil followed by wax.