Thank you again for your interest, compressor. As a lifelong snorkeller, never a scuba diver, my intention was to focus on basic diving gear, firstly because I believe diving historians have tended to neglect the study of fins, masks and snorkels, and secondly because I lack the specialist knowledge of regulators and tanks necessary to write about them with authority.
However, I will make an exception this once.

So far as I am aware, the "Medi Hydromat" is the name of the East German regulator that is best known in European historical diving circles. There's an excellent Czech-language web page about the device (below), complete with pictures of all the parts at
VSC - sbírka potápěčské techniky:
Czech isn't one of my foreign languages, although I visited Prague, Brno and Bratislava during the 1970s. If you're interested in the content of the web page, copy (ctrl-C) the text and paste (ctrl-V) into Google Translate and you'll get a rough translation into English.
Excellent sources of information in German about the Hydromat are
Das DTG Hydromat,
Hydromat 62004/2+1 and
Zweischlauchregler. The latter web page comes with a translation button.
I hope these three sites are sufficient to whet your appetite about East German breathing equipment!