I found this in a Riso HC5500 blog and as I have not seen it anywhere else, I thought the Riso multitudes might be interested. Also kind of explains the model letter meaning.
RG Series - RISOgraph 1986
RC Series - RISO Connected 1988
RA Series - RISO Advanced 1991
GR Series - Greater RISO 1994
TR Product - Tiny RISO 1994
CR Product - Compact RISO 1997
FR Series - Finer RISO 1999
RN Series - RISO Networked 2000
RP Series - RISO Printer 2001
V8000 - 2-color one pass 2002
RZ Series - RISO Ultimate 2004
HC5000 -Full color printer 2004
MZ Series - 2 color single pass 2005
Linear Mode
