[blazejos]

They were more different types of german Beton Panzer's

Pz-II turent with 37mm gun https://www.reddit.com/r/TankPorn/co..._were_rearmed/
https://forum.odkrywca.pl/topic/4209...rturm-zagadka/

And here a short article about usage of them in Berlin with photos
https://www.tapatalk.com/groups/miss...n-t318133.html

Based on this article we can say that first country which used tank towers on static fortifications was France in 1940 on Maginot line with old FT-17 towers. That is where probably Germans learns to build such bunkers.
https://laststandonzombieisland.com/...ortifications/