@meino That is quite a photo gallery. Some are '34/'35 Standards (identical appearance) and others are '34 Master The 2-tone Gray one is a '34 Master and is positioned to illustrate the obvious differences. Look at the "Fatter" appearance of the rear fenders. The black and white copied picture of a '34 Standard tourer with the Green '34 Master tourer to its right makes a good comparison of the two. Also note the presence of chrome mouldings on the hood and running board of the Master. There are also 1935 Master Tourers and 1936 models in your lineup These were not produced for domestic sale.

Your Opel engine is a mystery to me. There has never been an American produced Chevy inline six cylinder engine that looks like yours so I can't speculate as to its age.

You can replace the radiator cap that is being used for a gas cap at most any auto parts store. The cap fits Most Chevys from 1928 into the early 1970s. If STANT brand caps are available there, the part number is G-23 or G-23A and possibly G-20

Mike