OK,just out of interest, is it true that the later models of the Roland Jupiter 6 sported a Midi Thru?

Not that I know of. Later Jupiter 6 models had a IN/OUT(optional thru) standard MIDI bus.
Pretty much like their JX stuff. 3 way MIDI connections (IN/OUT/THRU) weren't really thought of as a necessity back then.

-ED-

Thought so, OK, thanks.

Confirmed here...noton a Jupee, nope.
Xtra hdwre. (min of a splitter) required on the way to the Jupee to keep assignments on going after it. The out is either out or thru but not both. The 106 has a thru and uses the same sound chip (Juno) althogh the timbre is substancially softer.