Export restricted (ITAR), sale only to US Citizens and Organizations. Pair of two Marquardt R-4A rocket engine nozzles, measuring approximately 4.5″ in diameter across the bell and 4.5″ tall, with one accompanied by an identifying tag: "P.N. 233363-450, Nozzle." The R-4A was an early prototype for the R-4D, a small hypergolic rocket engine designed by Marquardt for use as a reaction control system thruster for the spacecraft of the Apollo program. In overall fine condition.