Ray - sorry, can’t help. Our gun shop was in San Francisco. San Francisco banned the sale of air guns either when I was a little kid or before I was born. Not part of the current anti-gun stuff; was due, I think, to property damage done with BB guns by kids. At any rate, I have no knowledge of them, and don’t know anything about the apparatus show. My first take was that it was simply an MG30 with a blank-fire adaptor next to some sort of tanks, and an MP18 or 28 (hard to tell from that picture) simply laid across one of them. On enlarging it, it does look like the MP is connected up to them. Beats me though. Never seen such a thing. Not covered in Chinn’s MG books, that i can find although the Solothurn gun is of course. I don’t have a lot of works on MGs - some, such as “German Machineguns”, books on the Brownings, Chinn’s series, etc. - since in my lifetime you have never been able to own an MG in California. They were, therefore, only of peripheral interest to me, so my library can’t have more than seven or eight reference books on them, I think. Sorry I can’t be of help.