At the international meeting of the "Historische Tauchergesellschaft / HDS Germany" 2016 in Neustadt / Weinstraße, I became aware of the fact that, also very few, SINGLE-STAGE COMPENSATED double hoses regulators exist. The special feature is, that the respiratory resistance is independent of the bottle pressure. When the regulator closes "with the pressure", the breathing resistance is higher when the bottle is full, and when the regulator closes "against the pressure" it is vice versa. I immediately buy a exemplar of this type, the polish "Kaiman", about a Polish classified ads platform. It was in principle well preserved and must be only slightly restored and above all documented.