Very Nice! 
DDR Kartonmodell?
Might be easier to build than some kits.
Is there a scale? The gun barrel can be the problem.
I don’t think so. for the gun barrel I’d think a dowel or a rolled up (several times) piece of paper would work. Whatever the modern paper kits do seems to work quite well, and they don’t cheat - they’re all paper.
Notice how they would even have you cut out the antenna and attach it, instead of just using a cat whisker. 
Aren’t those curly?
No, cat whiskers are usually straight.
My late dad often told me that he build a paper model of a Vickers Wellington in the war. He said: “Wackere Jungen bauen sich ihr Spielzeug selbst”. He also had several plans for ship models in a drawer. How thick is the paper? Is the ordinary writing paper?
Curious choice - Wackere. I do not own these. I found them online while researching something else. That’s usually the way it goes…
But I can say this: If I had been a kid in the DDR I’d have built the hell out of these. I’d probably have bought other issues of Soldatenpost to get more.
The language of the 1930`s.
wacker = brave
From being awake, attentive, watchful.
There are TONS of paper models out there if you desire, and in all subjects. If you get into it seriously, there are different weights of paper to use, different building process’, different ways to color/paint, and different glues to use. It is it’s own legit hobby. We have a guy here in MN who does a lot of Real Space paper rockets…they are seriously impressive and very hard to tell from plastic kits.
Just one source of card models:
I know the word. It’s just very old school as H-H said.
I posted for the benefit of others