Wally and Steve — thanks for the “don’t” on the stones! I removed them from 45 sheaths today and found a stain similar to the 4th stone in Steve’s picture on about half of them.
If you have any of greg gutchers custom sheaths do not try to do any maintenance on them , especially the ones with hair.I took mine to a taxidermist and had them refreshed once when I thought they needed attention. They know what they are doing. Don't take them during deer season or you won't see them for months.