SG 503, often needs main frequency range C'AM switches fixed.
Requires special Tek cable for cal into 50 ohms
SG504 needs à leveling head
PG 506 rare and costly, see epay. Often needs repair or cal
PG506A can be $700..2000 see epay
The TM 5000 mainframe takes a 3-4 wide CG5110 that combines the functions of all the TM 500 plugins for cal
Bon chance
J
Jean-Paul