With all the talk recently about Deadwood chips, ivory were the original chips used there. Chips are available for trade for other ivory or crest and seals. BTW the scan shows a 3 chip matching set that is quite rare (flower bud, $5 & $25). I don't believe more than 2 or 3 collectors have this set.

P.S. Ivory would make a quantum leap upward in quality for you LE collectors!