OPNs or Orcutt Police Nunchaku have been around since 1985.
Very few depts. back then, picked them up. The only major depts. that I was aware of, that regularly used them were the San Diego and Denver sheriff depts.
After I got off of AD in Jan of 88, I was hired on with a private security company and we carried the OPNs. I actually preferred them over the PR-24. Primarily for their compact size and the fact the were always on your duty belt in their own holster, unlike the PR-24s were you had to take it out of it's ring every time you got in and out of your vehicle, plus the added bonus of, if you ever had to run, the OPNs were in a holster, whereas the PR-24s were slapping you in the thigh/hip/ass.
Haven't seen them much on the streets, but have seen several correctional depts. that still use them. Their compact size and design make them a good subduing instrument, which is a benefit in jails and prisons.
Here is their latest generation ....
http://www.orcuttopn.com/