I just bought one of these used... 5MC cart is standard.
I think it got a bump in transit and needed a little disassembly and jiggling to get started again - no idea what I did to make it work!
Anyway, I find it technically fascinating and very amusing too. Just the playing the record is fun, and I actually rate the sound pretty highly. Detailed, if a little thin compared to my conventional Pioneer PL-930 table. Mine has lost it's original feet, and has some inferior ones in the wrong place instead, so I'll find some new ones to try and improve the isolation.
There are videos of them on youtube. Basically, you open the front door, then press start/stop and the tray comes out. There are switches to sense whether you have put a 7" or 12" on it (haven't tried a 10"...). If there is a record, pressing start/stop moves the tray half-way in, and the tonearm swings out from the back of the unit. Start/stop will stop it again. If there is no record in place, start/stop closes the tray fully. Good fun.
Unfortunately the arm is basically unadjustable so cartridge choice is likely limited to the 5MC or something identical.
What I am wondering - if any Pioneer buffs know - is where this table was intended to fit in the line-up? It seems closer to a mid-fi design (albeit sturdily built and with a nice sound), but it is so small (12" wide and little more than 7" deep) that it wouldn't fit neatly in a standard seperates stack.