At least the three german "pocket battleships" (Spee, Deutschland - and I do not remember the third name perhaps it was Scheer?) all had three gun turrets . Nevertheless, as Ron already has stated, this etching is a "reproduction" (pure phantasy) one.
after your for and against info I hope Mr. Wittmann can solve the problem once and for all, has he ever seen a KM with a battleship on the blade? I have not his book on the subject anymore.
These "battleship" blades often have the Eickhorn logo etched, although other makers also produced these post war blades. As Ron pointed out, this is a repro fantasy blade. The only Navy dagger I have seen with a ship etched is the rare Klass Naval blade with the U Boat etch.