I used to own a Bronco SQ-Ai 6x6cm roll film camera. This camera had removable backs so that you could fairly easily switch between say 64 ISO slide film and 400 negative film mid roll. To be able to do this, each film back had two dials on it: one for ISO and one for exposure compensation. When you attached the back to the camera, the information was communicated by a set of contacts to the metering prism. There is something so delightful about that window of time when cameras were becoming electronic but still using film. So many clever things were happening. I think about the Canon T90 that the presenter in this video mentioned: it was a technical marvel with lots of different metering modes, a digital display, etc. ...or cameras like the Rollei 6008, which had incredibly sophisticated light metering and film handling, yet still used an analog waist level finder.