The helicopter used for the train heist (N3105G 1958 Bell 47G-2 s/n 1875) is a very special one. It is now on display at the Classic Rotors Museum in Ramona Airport Hangar G, Ramona, CA. in San Diego County.
Kathleen Freeman was reunited with Leo G. Carroll in this episode of UNCLE. They had appeared in Topper (1953), in which she played Katie, the housekeeper, to Carroll's lead character, Cosmo Topper.