Hi Zoli, it's quite different to the Japanese First Plate folder (look at the handle, front rise etc) and these wouldn't have been exported to Europe anyway. Before WWII very few Japanese cameras were sold outside Japan itself and then mainly to other far eastern countries, only Hansa (Canon) were begining to sell world wide at that point.
What doesn't help is at that time some cameras were made without a makers name and were often badged with a store or distributors own name plate. In the UK Wallace and Heaton used the name Zodel on equipment they sold and there were many other similar rebrandings in the UK/US and I'd guess Europe as well. This make identification difficult.
What may help you is Schneider were still a smalller lens manufacturer at that time so their lenses were less common and used by fewer manufacturers. They seem to have benefitted from Nagel's leaving Zeiss Ikon and setting up on his own again (He had previously founded Contessa Nettel). Look up the Radionar's serial number as that'll tell you an approx date when the camera was made.
Good point about serial number. Thanx a lot.
Unfortunately i don't know very much about prewar cameras. Thanx for your advice about japan plate folders, also