An R-4D Reaction Control Engine purge plug. Plug measures 15″ long, with the metal parts bearing stamped and stenciled part numbers, with a hard rubber collar at the bottom of the flexible base labeled “Durometer 60/70.” The R-4D and this type of purge plug were use on the Apollo Service Module and the Lunar Module. Scattered light wear and some small areas of light pitting to metal pieces, otherwise fine condition. RR Auction COA.