@ Denis.... The below comments peaked my interest as well, so I browsed the internet and found the following info on "Fathom World" site.........

"The asymmetrical stern, which consists of a slightly twisted aft shape, was conceived by German shipbuilding engineer Ernst A. Nönnecke in 1962. It was thought to provide better propulsion by taking into account different flow conditions either side of the propeller.
Compared with traditional sterns like the elliptical stern, the cruiser stern, or the transom stern, model testing has shown the asymmetrical stern is capable of producing fuel savings of between 3-6%. The asymmetrical part means that the stern frame is turned in the opposite direction of the propeller action. This generates a swirl to the flow ahead of the propeller, which counteracts the rotation of the flow from the propeller, reducing energy loss".

Source: "Fathom World" site

What are "asymmetric stern frames"?

Hello Axel, the first ship with asymmetric stern frames was THEA S. (IMO 8120856) in 1982 acc. to publications available. However NORASIA SAMANTHA, having also asymmetric stern frames, is remarkable because she was the first 'Ship of the Future' developed by HDW Kiel, having many features improving the operation of ships.

If I remember correctly the first ships with asymmetric stern frames?