Wanted: Shimano 600

you want the AX not the EX then.

Sorry to be a Shimano geek, but there are four versions of 600, listed here from cheap to pricey:

• original plain 600 with black "S.I.S" rear derailleur
  
• 600 tricolour
  
• 600 Arabesque (EX)
  
• 600 AX, parts have blue logos and 80s "aero" geometry