i have tried with decent success using a wide variety of finishes - tung oil, linseed oil, danish oil, oil and water based poly (but no shellac.). thinned, not thinned, sprayed, aerosol can, brushed and wiped on. even heated - in more than one combination of those. even Osmo - so far that stuff has impressed the heck out of me, used on a pecan slab dinner table and its unreal .

but for the best seal against atmospheric (not direct water) moisture for a chess board (walnut and white oak or hard maple) i was thinking heated eoither danish/linseed/pure tung oil thinned 50/50 with mineral spirits. at least 3 applications after each coat dried and sanded at 400 grit. then 3 coats of minwax poly matte.

over/under kill or maybe even just plain stupid?

shying toward danish oil for drying time - raw tung oil can take a while