The Poseidon Cyklon 300 second stage is definitely one of my favorite second stages. I don’t particularly care for the first stage.
I have actually paired up some Cyklon second stages with a Conshelf first stage and it works well, but I have to run the IP about 170 psi.
One of the projects in my “to do” list is to change the demand valve spring on some of my Cyklon second stages so they will work with a more conventional IP (about 140 psi).
I starter repairing Cyklon 300 around 1971, during my first job in a dive shop (I was 14 at the time).
In the 70’s the Cyklon 300 was my favorite single hose regulator. It has always been a bit of a process to adjust it with its unbalanced first stage, but I always liked that second stage.
The reliability of a Cyklon is very good when it is working well, but again it will not come close to an Aqua Master, a vintage Mistral, or a Royal Aqua Master. Any of those double hose regulators are known to go many years without needing service.
Here are some of my Cyklon regulators. The short first stage has only one LP port for the second stage; that is an original Cyklon (predates the Cyklon 300). I don’t have that regulator anymore. I actually traded it for an Aqua Master. From a collector stand point that first stage is far more unusual that an Aqua Master, but I am more of a diver then a collector.
I also have a couple of sets of Poseidon tanks:
But when it comes to deep diving here was my equipment of choice just a few years ago.
You may be able to see the max depth indicator needle at 200 ft.
I have owned that Royal Aqua Master since 1971.
Added:
Nemrod
A couple of the guys from one of my favorite LDS just came back from the Oriskany and they said that with the hurricanes it has settled and the deck is now at 150 ft. That was confirmed by several divers and the dive master. The boat captain mentioned that they were the last “recreational” divers to dive down to the deck.