There were three versions of this, although one could be converted easily into any of the others.
MZ-811 : The basic model with no built in peripherals. This came with a blank cover.
MZ-821 : With built in 1200-baud tape drive.
MZ-831 : With built in tape drive and printer-plotter.
The tape drive could be substituted for a Quick-Disk (QD) unit. The Quick-Disk was a small, 2.8" disk with sequential access.
The MZ-800 sold in Japan as the MZ-1500 which had a black case, black Quick-Disk unit and slightly different graphics environment.