Interesting read. Some nitpicking as a born East-German: In my opinion, the last row of images shows pretty standard UW-orienteering equipment, which has not mu

Interesting read. Some nitpicking as a born East-German: In my opinion, the last row of images shows pretty standard UW-orienteering equipment, which has not much do with Boettgers scooter-like device. In particular, it has no engine parts, only air bottle + navigation (compass and distance counting meter) https://en.wikipedia.org/wiki/Underwater_orienteering https://en.wikipedia.org/wiki/Underwater_orienteering I'm quite sure, because I was involved in this kind of sportive activity during the eighties and nineties of the last century and have build this and similar equipment myself.