We have a rogers tube sub sheet in the reference section
It lists the 89s ,and shows an 89 as being a sub, but not the 89RS as on the schematic.
The Nostalgia air tube data for the 89 is here listed as a Triple Grid Power Amplifier
https://www.nostalgiaair.org/tubes/89.htm, it doesn’t look similar.
Most rogers tubes of this era ended in an S or an M , usually the ones ending in s are grey and the ones ending in M are black. someone correct me if I am wrong, I figured that It might have signified that the tube was sheilded or metalized.
This tube ending in RS seems very unusual to me, hopefully someone will chime in with more info.