I use just vintage demand valves (2nd stages) from old Soviet (Ukranian) scuba, named
Ukraina-2 with modern 1st stages
I use it for many years, and it is the best in my opinion. Most simplest ever seen, most reliable, most lightweight.
There is really original hoose, that looks like from garden
Because originaly intermediate pressure is less than 7 bar. And yes, this valve is counterflow.
just five main pieces - hull, seat, nail and membrane, and exaust valve
Also I do like old Soviet (Ukranian) fins from Kievguma - Akvanavt. I had it when I was a schoolchild, later we lost most of out own (due to war in Georgia), and now I again found it! Original! With printed price 8 rub 50 kop
It is soft and very powerfull.
Sometimes we just kidding and use some reworked old equipment, but not for regular diving, but for fun, like:
sidemount from one of the first soviet scuba AVM-1m
It is very nice!
When you are swimming - you can shake to left and right, and your lungs will automatically be inflated and deflated, due to level difference between big membrane of demand valve and your lungs.
No extra force required for breathing in this case!
very nice.
old Soviet and rare compass KNM, and depth gause G-5. I has it, but not use (Oceanic computer and Scubapro compass is more comfotrable
)
UGK-2 Soviet dry suit.
So, now your know one more, who love vintage equipment.