The G 12 was based on the Prussian G 12.1 and a 2-10-0 locomotive built for the Imperial Ottoman Department for Military Railways (Kaiserlich Ottomanische Generaldirektion der Militäreisenbahnen or C.F.O.A.) by Henschel (see Prussian G 12 (C.F.O.A)).
The locomotives differed in several points from earlier principles for Prussian locomotive design.