The closest I've been able to come to matching this is some sort of Ektachrome that I know it can't be. I haven't used Ektachrome since the 80s and this was in some Mido holders I loaded 5-6 years ago, IIRC. It has to be some version of Astia or Velvia or other Fuji transparancy film available. But it doesn't match up with internet resources I've found so far. take a stab