This reminds me, years back I picked up an NTT Data Super Famicom Controller [0] with the idea of adapting it to USB. An off-the shelf USB converter only handled the standard SNES/SFC buttons and completely ignored the number pad. At the time few resources even mentioned the existence of this thing, so I put it on the shelf and promptly forgot about it for other projects.

[0] https://www.raphnet.net/divers/ntt_data_sfc_controller/index...