Essential technological development stagnated at the C51/D50 level, and after that a certain degree of improvement of boiler pressure and partial improvement of the electric welding adoption, etc. were made, but most one-off introductions of essentially new technology failed because of a lack of consideration on the part of the development staff.
本質的な技術発展はC51・D50の水準で停滞し、以後はボイラー圧力のある程度の向上や電気溶接採用などの部分改良が成功した程度で、本質的な新技術の単発導入は開発陣の配慮不足もあって大方失敗に終わった。