My friend just picked up a 1918 icebox with an oak exterior. It is in original condition and he intends to leave it that way, but he would like to preserve what is there. Could you give me some advise on a good finish to put over the existing that won't change the color too much but make it look nice and keep the wood in good shape. I'm not sure if I need an oil, a wax or what would work well. Thanks.