Said to be from the Washoe Club, Virginia City. However, the only listed Washoe Club for VC opened and closed in 1945 (TGT, Audit Copy p. 336) far too late for ivory chips. The etching around the rim is cruder than the "5" etching. That chip appears to be a IN-UR (Variant?) in Dale Seymour's book, Antique Gambling Chips. Even the ink in the 5 and the circle appear to have been added. Two knowledgeable chippers are on it - though the current price is not unreasonable for an IN-UR "5" ivory. There are a number of recently reproduced ivories being sold on eBay. I bought a "25" for my collection but the dealer acknowledged that the genuine old ivory chip had been etched by him. This dealer claims it came from the "Washoe Club."

http://cgi.ebay.com/Old-West-Washoe-Club-Virginia-Nevada-Ivory-Poker-Chip_W0QQitemZ6249866987QQcategoryZ63752QQrdZ1QQcmdZViewItem#ebayphotohosting