A little off topic, Danube Class

[MikeW]

I was reading an article about Herman Goering in WW2 magazine.
When discussing our liberty ships, he mentioned that Germany took 9 months to build a single Danube class ship.

What was the Danube class and what did it look like?

Tried to google it but flooded with trekkie stuff.

[Dietrich Maerz]

The only thing I could find is this. The ship "Donau" (Danube) which is a submarine tender. Tiemframe 1939/1940. I couldn't find a "Danube" or "Donau" class of ships.

[MikeW]

Quoted from the article
"It took nine months to build an "Danube" vessel"