This was the forerunner to the sidetrusters.
One vessel built in Norway for a Faroese owner the Skugvur had one fitted as she was a purse seiner.
I am norn sure if another Faroese purser the Asur had one ????
In Iceland the first fitting to a commercial fishing vessel was on a vessel named Hofrungur III
The rudderstock was hollow containing electrical cabels for the electric drive motors for the Pleuger propeller.
Photo could well be of the Skugvur as her CPP looks like one from B&W-Alpha who did supply engine and propeller to the Skugvur!!!!
The cable ships "Monarch" and "Iris" built 1974/5 were each fitted with Pleauger rudders to give fine control and manoevring at slow speed. Quite effective but under powered, superceded by stern thrusters and azimuth drives!