i've only ever seen them twice. one my boss had and 1 on site at a engineers office.

one of those obscure pieces of hardware around before the internet and apart from a few photos on auction sites doesn't exist online.

https://www.tzsupplies.com/modular-technology-mt25-iv-interf.../

and a 1 page pdf of the manual. https://docs.rs-online.com/e9af/0900766b8001aeab.pdf