Hi guys and thank you for the varied answers. I guess that the regulator breakdown may allow you to get down to the identification. I must say that this first stage is weird. I have disassembled a few first stages of different brands but many things in this one seem odd:
+ All O-rings are colored and different colors, even the high pressure seat is blue
+ The holes in the seat retainer to unscrew it are smaller than the standard MK V so the Scubapro tool did not work and had to improvise one
+ The retaining ring in the DIN coupling simply broke when I had to remove it without no apparent force (not more than usual anyway), visible in the picture
+ The swivel retainer has a non-standard hex key. The 3/16 that works in the MK V is too big. I tested with metric hex keys and the 4 is too small and the 5 is too big. It could be a metric 4.5 but I do not have that one
+ Paying attention to the DIN main part you can see that the hole through it is not even concentric to the piece (see the detail picture) and the interior is not chromed
All in all, the clone suggestion seems to gain strength, I cannot think that Scubapro or Tusa would produce this low quality piece.
Again, all your thoughts or suggestions are welcome. Best regards
Jordi Altimiras