Used to load the encryption keys into secure telephones (see my rendition of the main hardware here - Cryptex 70 (https://www.artstation.com/artwork/xJZr12) The male / female outputs on this gear is standardised and thus can be plugged into other cool spy tech. This project was done as practice for higher polygon count hardsurface work.
Thanks to Cryptomuseum (https://www.cryptomuseum.com/crypto/philips/spendex40/index.htm) for some awesome reference (their whole site is worth browsing if you enjoy cold-war spy tech and more!)