Japan uses NTSC (well, used, since Japanese analog TV has all been turned off now) - it's slightly different on a technical level from US NTSC, but it will display anyway. Assuming that console is the same as the SCPH-50009 retail version that console outputs a video signal that's the same as NTSC:J (I.E. 0IRE black level), but the discs are region coded for China. That's also the reason for the 220V power supply, since China uses 220V.
I would guess they are extremely uncommon - there were only about 10 games ever released with that NTSC:C region code and the "official" China consoles never sold well anyway because modchipped grey import units were cheaper and could play a much wider range of games.
Initially, there were no modchips, but later on someone produced a hacked version of the Matrix Infinity that was compatible with the boot ROM and mechacon in these consoles (it was called "Great Dragon" - 大龙) and the sales of legit games dropped even further.