[Hallicrafters] Identifying SX-101 receiver model

[K7VS Van]

I a couple of SX 101 receivers which are SX 101 Mark 2 and Mark 3 models
have had been stamped inside on the top of the chassis with a serial number
and "Mark 2" and the other with "Mark 3" between the large bandswitch cover
and the xtal calibrator.  You might take a look inside the top cover to the
left between these two things and see if yours has a stamped directory on
the chassis with this information otherwise you may have a plain vanilla
101!

Hope this helps.   Van, K7VS