Bama it's a thermo 3500 DIN http://www.thermovalves.com/scuba_outlets.htm
the last one on the page. It's a pretty small neck not exactly sure what size. If you have a K valve you think would work at high pressure I'd be happy to switch. Just one question, normally an o ring blows when taking off the reg or just turing it on, or can it blow when ever?