The Reich Air Ministry used an internal designation system that included a prefix number signifying the engine type, 9 for piston engines and 109 for jets and rockets, followed by a manufacturer's code, followed by an engine series number.[1] Unlike the 9-prefixed piston engine designations, the 109-series of reaction-thrust, turbojet, turboprop and rocket engine designation numbers' three-place numerical suffixes had no "firm adherence" to any one manufacturer.