Hi Doug in Munchen, that is a nice boat you are restoring! By chance I watched a film called Suicide Mission. It is plotted around these boats and must have been made just after WW2.
The unusual thing is the engine sound you really can hear them coming as it is more like a gas engine with staccato bangs from the exhaust. That feature is even mentioned in the plot to identify one.
I have a Naval Intelligence identification book issued to ships operating in the N. Sea dated November 1942 and there are several grainy B/W photos of the fishing boats.
In all the pictures it shows the large winch mounted fore and aft. Much more logical when you consider the arched net haulers where the trawl boards are located.
Also not to forget the buoy carried attached to the shrouds as this is part of the fishing system.