I see one on Ebay.
It appears to be a print automation device that will help you make "machine prints".
You would aim the sensor at the middle of the easel, then make the first print setting the coarse and fine dials until that print looks good.
From then on, you put the next negative in the carrier. Push Expose, and make print after print from different negatives, with this device making every print "on average" the same as the first one.
This might help in a production print process, for example if you wanted to print every negative of many rolls of film. It may have been useful in a consumer photo processing facility.
Now, I don't want to discourage you if you are interested, because it might be a fun experience to try to make it work.