Polyplast

Old ad for the lens kit scanned by Uwe Kulick  (Image rights)

Dr. Staeble's Polyplast-Satz was a lens kit for folding cameras. It allowed to assemble lenses by mounting one back element on the back of a shutter/iris assembly, and a front elements group on the frontside of the same shutter. The back element stayed fixed, the front element group could easily be exchanged by another since it was fixed on a special fast mount.

Links

• The advertisement above mentions the famous "Belichtungstafel nach Dr. Staeble" which could be ordered from Staeble for 50 Pfg. Here is a link showing an example of that written exposure aid of times before EVs could be measured by everyone with meters:
  Belichtungstafel nach Dr. Staeble at Fotoamateure Teublitz [1]