The Model IV was the last of the series (and probably the lesser known) even though it was clearly the best. Similar in appearance, it was the successor of the Model III but could run the majority of its software.
The standard version included 64K of RAM, but you could buy later models that had 128 KB (the upper 64 KB being used as a ram disk). It has one or two 5.25" floppy disk (184 KB each) and ran under TRSDOS 6.0 or 1.3, LDOS or CP/M and featured a 12" green screen.
An upgrade kit for the Model III to make it into a IV was available, and the Model IV
was followed by the Model 4D. The only difference was the inclusion of double sided drives (384 KB per disk instead of 184 KB).
A portable version of the Model IV called Model 4P was also marketed although not very successfully. The Model IV was blown out at clearance for less than $600.