"I am not sure, but looks very close to Centaur rear mech. I have some catalogs (German shops Rose and Brügelmann) from year 1990 and 1992. Centaur deraileur in those looks VERY close to that in a picture. It might be from year 1992 since cable attachment is with alley key nut. In 1990 models cable attachment nut is for normal spanner (8 mm ?)"
Late '80's. Possibly Chorus, Croce d'aune or Corsa Record. My memory isn't too good for the differences between them at that time.
It is definately from that era because the shroud for the top pulley was drilled out on the early '90's onwards models.