I picked up a 1978 Buck 500 on the auction site a while back. The knife's in great shape and the sheath is in pretty good shape except that it is very dry and the surface has fine cracks which become apparent when flexed. I tried some leather conditioner on it, which restored the luster of the surface but of course did nothing for the cracks. Is there anything that can be done for leather in this condition, or is it too far gone for restoration?