maybe it has a different speaker than one without the badge (JBL vs non JBL)?
It actually looks like that's the reason. The June 1969 price list shows for the first time the "Standard" models, the "D" used JBL D-140F speakers versus the "S" used "heavy duty special design speakers".
The November 1969 price list adds the T-Star Bass Spkr System as standard version (vs the JBL and ElectroVoice versions). The complete amp (right) had the "Standard" in the name.
Same for October 1970 price list.
I have no 1971 price list but in the April 1972 price list they were no longer offered.
Ralf