I have two very similar Esselte Studium counters (half-height compared to the pic, but otherwise identical style and colour scheme etc.), both given to me as faulty. One has Nixie- tubes, other has 7-segment LED-displays. The connectivity looks very similar, bunch of DINs on front panel.
One similarily styled accessory (a Geiger-sensor PSU box) I once had a look was dated JAN 1979 (sticker inside) so I presume this was a late 70's/early-80's series of school measurement instruments.
I have seen these used with Geiger- sensors to measure the number of clicks within a specified time (TIMER SEC. in pictured unit). The system included a counter, a Geiger-sensor with it's PSU box and an external speaker. The connectors on the left let you connect different kind of sensors and an external start/stop- signal.
If yours has a multimeter functionality, that would be actually quite nice as a bench meter unit. (I presume that if you select "DIGITAL" the display will show the measurments from the multimeter-side). Don't know how much use the counter would be, though.