Realistic Concertmate MG-1 
An analog polyphonic synthesizer manufactured by Moog Music in 1981 and sold by Radio Shack under their ‘Realistic’ brand name, it is perhaps one of the most widely owned of all vintage Moog synths. It was produced without some standard Moog features, such as pitch and modulation wheels, as a cost-cutting measure aimed at achieving a lower price for the consumer market. The MG-1 is a 2-VCO monophonic/polyphonic analog synth with a genuine Moog filter, however the overall sound is thin compared with other Moogs. The synthesizer also featured a pair of pass-through RCA jacks, which allowed users to mix radio or records into the final live synthesized sound output.
On the MG-1, the VCOs are referred to as 'Tone Generators'. It can produce sawtooth, square and pulse waveforms, and the oscillators are detunable and syncable. An ASR (attack, sustain, release) envelope called 'Contour' can be applied to both the amp and the filter. There is a Ring-Mod effect called 'Bell'.
Unique to the MG-1 is a slider on the far right side of the keyboard which controls the volume of a simple divide-down polyphonic organ sound. .
Notable users: Peter Gabriel, 808 State, Brian Jonestown Massacre, Tame Impala.
References: Wiki, Vintage Synth Explorer, Encyclotronic.