Detector for Beta/Gamma Monitoring.  Works with the AMS-4 air sampler. Model number YP11562043.  Has a bracket to allow mounting to a wall, or you could place it on a shelf.  You will need a cable to connect to the AMS-4.  These have some shielding around the detector to reduce background.  They weigh 14 lbs!

The photo is one of the units.  They are all the same, with different serial numbers.