Motorola R-1013A Sinad meter AC/DC radio tuning

Motorola model "R-1013 A Sinad Meter". It is marked on the back for AC or 12 volts DC. We plugged this in to the AC cord and it powers up. We don't know much about this. It's from the estate of an electrical / industrial communications engineer and ham / shortwave radio enthusiast.

Item No. n210419