Micro Switch 12SW1-1
The photos below are archived from eBay listing 224236125922 “Vintage Micro Switch 12SW1-1 Keypad Keyboard 12-button A123 STOP SEND MSG 1970s” from seller highvoltagemary; the original listing has since been deleted by eBay. This is a 12-key keypad with no electronic components present on the PCB (besides the Hall sensors). The production date is 1970 week 40, which at the time of writing is the earliest-known keyboard with 1SW11 switches (replacing the original 1SW1 model). The PCB was designed to take a 24-pin header, with dedicated connections for each output of each of the twelve switches. However, each pair of outputs has been connected together, and the unit was connected with flying leads that have since all been cut short. In addition to the 24-pin header, the PCB expects separate +5 V and ground wires.