SHELF ! underwater laboratory

[aukepalmhof]

In 1968 in the former Institute of Oceanography and Fisheries, together with the engineers Harry Amörkov, Valchan Valchanov, Iliya Krastev, Ilko Ŝirkov, and Traian Trayanov developed the Bulgarian underwater laboratory shelf 1 and conducted extensive scientific research.
Source Internet.

Navicula gives for the SHELF 1,
Underwater laboratory "Shelf 1": ... was built in 1970 by the Research Institute for Oceanology & Fisheries, Varna. The laboratory consists of 3 sections that serve as storage for diving equipment, as a lounge and as a workspace. It has a metal foundation that partially serves as a tank for solid ballast. The water ballast tanks are used for vertical movement. Oxygen and electricity are supplied by a surface ship. Food is lowered to the laboratory in a special container. In 1970 tests were carried out at 70 'depth in the Black Sea. A crew of 3 men stayed underwater for a total of 7 days. They worked outside the laboratory for 4 to 5 hours a day.

I found a photo of her on the internet when she is out of the water, and it looks that she is a museum piece. Behind her, you can see the camera lift depicts on another stamp of the series. Have not any information on the camera lift. I don’t know where and when this photo was taken.

Bulgaria 1973 2s and 18s sg2215/16 scott?