I was invited to 'make up numbers' for a weeks diving with a dive club [I am not a club sort of guy] , 16 in the group, 13 were diving RK3 , even the skipper of the dive vessel said 'what's with the RK3s?' in a whisper to me as I know him, it's a club thing , I think, I said.
The other 2 not wearing RK3 were also not club members, Mares Avanti Quattro for them.
I dived Scubapro go sports that trip, I was the only one using Scubapro regulators and BC also, out of 16 divers that is rare here, the 13 had Apeks or Aqualung regulators, the other 2 divers, Mares 15X, I think they were.
I will not name the 'club', like a uniform, it's what they use, not my scene at all, all trained buy the same 'agency' also, again, no names no court martial.
I have RK3s and they are not used now, going on eBay now.