This used TG500 is fully functional & in good condition.
The TG500 is basically a box-o-sounds. It is based on Yamaha's SY85 (1992) and doubles the polyphony but loses the sequencer and most of the buttons and controls for real-time and patch editing. You can go with just the stock sounds, their sound quality is excellent, using AWM2 (Advanced Wave Memory), Yamaha's synth-engine of choice since the days of FM-synthesis. You can also add external ROM cards for many more sounds in various styles. Despite the lack of controls, the TG500 has edit capabilities as extensive as the SY-85, and is easiest to program using an external or software based editor.