I found a few of these in an antique store down the valley a few years ago - not far from Sonora. They were in a rack with a bunch of generic plastic chips. Later on, some turned up in Washington and were used as drop chips. At least that is the story I heard... Here is a link to the page in the ship guide:

http://www.chipguide.com/cgi-bin/search/search.cgi?id=wachde