Very cool Humi! Please check out this thread for seasoning info:
http://www.cigarasylum.com/vb/showthread.php?t=620
Also, before you start seasoning the humi I would recommend placing a bead of aquarium or food grade silicone sealant around the glass-to-wood-seal on the inside of the lid. I would also put a bead around the hygrometer where it meets the wood inside the lid. Both of these seams can be sources of leaks (and much aggravation) down the road.