I will have to get back systematically to 1925/1926 in order to find whether the neat rhomboid surface structure had been there from the beginning OR that we have to reconsider our presumptions about this type of paper at all!
To give a small hint! What about the watermark being pressed in the paper from the back??? At the same side as the rhomboids????
No matter whether the Austrian paper exist or not! It probably does but I will love to meet someone who can sell me one for $ 4
The WT paper has a soft surface at the back with plenty of rhomboids BUT it also has a relief of the watermark!!!
At the front you cannot see a bit of relief should the watermark have been applied from there !?!?!