That's a nice clean up you did there.
I think the original designer got their wires crossed a bit. The model looks to me to represent the WWII type VIIB.
There were two U53's commissioned into the german navy.
In WW1 U53 was a type 51
In WW2 U53 was a type VIIB
https://www.uboat.net/wwi/types/?type=U+51
https://www.uboat.net/types/viib.htm
Sorry to be a pedant.