Pictures of Perka
Pictures attached as mentioned above.
Interestingly there is a very similar camera for sale at the Leica Shop (Westlicht Auctions):
Their model is different in that distances are actually marked on the focus wheel, so it looks like this camera has been specifically set up for use with the 180mm Tessar shown. It also has just one focusing wheel. On my camera there is a second wheel which acts as both a focus wheel for left hand use or by turning backwards as a focus lock. My camera has no distance scales marked anywhere so I guess it was used solely with GG focus.