Short Empire "C" Class
Initial production run as the S.23. Second production run differing only in model and hull strengthening as S.30, and final production of only 2 aircraft as S.33.
Some aircraft were impressed for military service, with two S.23 aircraft modified with gun turrets and ASW radar as S.23M's. Shorts quickly modified the design to become the military S.25 Sunderland, which was eventually re-civilianized to become the Sandringham.