CPU: MOS Technology 8500 (a modified 6502 with an integrated 8-bit I/O port) @ 0.985 MHz .
Graphics: MOS Technology VIC-II MOS 8569 (PAL).
16 colors, resolutions 320×200 and 160×200, 8 hardware sprites, 24×21 pixels.
Sound: MOS Technology 8580 "SID".
3 voices, ADSR programmable. 4 Waveforms: Triangle, Sawtooth, Variable Pulse, Noise
Oscillator Synchronization, Ring modulation.
Programmable Filter: High Pass, Low Pass, Band Pass, Notch Filter
Memory: RAM 64K. 0.5K Colour RAM. 20K ROM.
Value: £70 - £150. Depending on condition, and if boxed, etc.
The Commodore 64 Games System, generally referred to as the C64GS is basically a Commodore 64 computer, with the keyboard and most other connectivity removed. You have the base unit, a cartridge port, two joystick ports, RF and Video outs... and that's your lot.
It was released in 1990 bundled with a four game cartridge containing Fiendish Freddy's Big Top O'Fun, International Soccer, Flimbo's Quest and Klax.
Like Atari with the XEGS and Amstrad with the GX4000, the C64GS was intended to hop on the successful 8bit console bandwagon, to compete with the NES and Master System, while using the existing technology of their respective 8 bit computers.
The problem with the C64GS, and the reason for it's failure, is that it offered so much less than a standard C64, with no other encancements to make it a worthwhile purchase.
The GX4000 had somewhat enhanced graphics over the CPC464, being a consolised version of the plus model computer, while the XEGS was basically an XE computer with a detachable keyboard.
So, with very little software created specifically for the C64GS, those who bought the system would reasonably assume that they could run normal C64 cartridges on their console. However, they often found themselves somewhat stuck when they plugged in said cartridges, as they'd be presented with an instruction like "press enter to play" or similar. Having no keyboard, this obviously made the game unplayable.