I added two new clubs to my collection of "Knockers". I now have them from the Mapes in Reno and from the El Rancho Vegas, the Sands, and the Congo Room at the Sahara in Las Vegas. The story I heard was that an entertainer - whose name escapes me - didn't like clapping at his shows so they provided these knockers for folks to tap on the table instead. Apparently it caught on and was used at several clubs. I don't know if there are other clubs or if these four pretty well complete the set. They are all came in a variety of colors so there are probably about 20 or so different ones to be had.