Ive never heard them called a slap jack but have heard them called a Blackjack or a Sap. The one i have that will never be sold is my early 1900's Winchester .22 pump that belonged to my great grand dad my grandma passed it down to me when i turned 18 was my first gun.I have a Colt Police Positive .38 that my great grandfather carried as a Railroad Policeman down at Adair Village during WW2. The bluing is badly faded but it locks up tight and I have fired it a couple of times. I also have the leather flap holster he carried it in, as well as his badge, laminated ID card with photo, wooden nightstick, and a nasty little weapon that I have been told is called a "slap jack" which is basically a lead ball wrapped in woven leather straps that tie off in a flexible handle about 8" long. One of these days I am going to buy or build a display case that I can mount them in and hang on a wall.