Started in '73 when all issue trousers had the sap pocket, in the southeast anyway. By the early '80s sap pocket was gone but sap itself was still authorized, just stuck it in the the RR pocket, yes it was a PITA

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Preferred the bell shaped blackjack myself over the slapjack. The flat slapjack was promoted as producing less cuts when used against the miscreants noggin, which it probably did, but only when the flat made contact. When the edge made contact, which often occured during a knock-down-drag-out, it cut worse, a lot worse.
Noggin wasn't my preferred target anyway, in fact I only used it on scumbags heads a couple times. A good shot to the collar bone, shoulder or forearm and they wouldn't be using that hand against me, during that scuffle anyway

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Funny, but when the sap was authorized, early expandable batons were specifically not authorized. Personally took to the ASP myself when they came out though, but I was already pre-disposed to the correct impact areas, and I learned to use the ASP well...very well

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There was a time in the late '70s and into the '80s that the police nunchucha became popular, in South Florida anyway. I'm convinced they whacked more cops than badguys before fading away...
What's that saying about sausage? It's great to eat but not something you want to watch being made. Unfortunately folks don't like to see what is often required to enforce the laws they want enforced. Impact weapons aren't always pretty.