I started in '81, and they were still in use by some (though probably not most) officers. I never knew anyone who carried the spring-loaded type with the weighted end. Everyone who carried them had the flat leather sap, of varying lengths. The longer ones seemed more "effective." I had one of the shorted ones, so it fit well in my back pocket if I had a pair of trousers without the sap pocket. (Although in '81, the Kel Light was pretty popular, and this became a "flashlight pocket" for the C-cell models!) Although I only used mine a few times, it was pretty handy when I did- once, when a drunk managed to grab my baton, and another when a drunk grabbed me and I couldn't get to my baton. Grabbing that little sap got me right back in control of the situation!
The department I ended up on in '86 prohibited them very shortly thereafter. The chief's rationale was that carrying them was "not the image we wanted to present." Personally, I disagree- most people would have no idea what they are, especially if they were discreetly carried, and so it would have no effect on our "image." And, for those who knew what they were, it would present the image that we don't mess around!!! (Any perp that's ever been on the business end doesn't soon forget it. Even the drunkest idiots seem to remember it when they sober up!) They were a great back-up weapon in close quarters, and when you had a bunch of coppers piling on trying to handcuff an uncooperative suspect, they were a lot easier to deploy that a baton or a PR-24. (On a side note, I never found the PR-24 particularly practical. When we carried straight sticks, I carried a short one with the metal ball on the end. When a suspect refused to put his hands behind his back, that little ball properly applied between the shoulder blades made it an almost involuntary reaction to comply!)