I've also seen that split head design from Riva but it was an o-ring head, no gaskets. If you open it up and find the domes look like a cooling fin design it could have been made by Riva for someone else. I had to change one of those heads on a friend's ski because the dome cracked. He was losing compression through the crack and it turned out that you can't get replacement domes for that style of head anymore so it has been sitting on the bench collecting dust for the last 5 years or so. As far as I can recall, those finned domes weren't very strong and this was a common problem. There wasn't enough meat in the dome structure and probably can't resist the compression for long before they crack. When I say for long I mean unlike an ADA dome where they're solid and meant to last for life against such a scenario. He did pretty well with his considering the head was put on 15 or so years ago but then again, he only gets out on the water about 1-5 times a year and on a couple occasions a year or two would pass by and he never got out once. My ADA head goes back about at least that far too but never had any issues with it to this day and until the last few years I was out dozens of times a year every year.