Fake or Frankenwatch...Omega Constellation

I picked up this Omega Constellation for $200. When I went to change the battery I noticed there was no Omega stamp anywhere on the movement. I know Omega used some outside ETA movements back in the day and I was wondering if that's the case with this watch or is this just an Omega that had the movement replaced with an outside ETA movementView attachment 969217 View attachment 969219 View attachment 969220 View attachment 969221 . I'll will refer to the experts...what do you think?