The OS2U-3, eventually the most widely known “Kingfisher”, was introduced in 1941.  This model had the latest P&W-985 (AN-2) engine, extra fuel tanks in the wings, and additional armor protection for the crew.  Vought produced 1,006 OS2U3’s.

OS2U:

Engineering Triumph and War Time Hero
Fisher of Men
One Kingfisher Saves Ten Men