It's fine. Here's a pic from a 1966 catalog (top right watch on the left page)
It's a ref 803 AD, but I don't know if that would have been stamped into the caseback, as "D" refers to the date complication. At worst, it has a case/casbeack from a nondate watch.
I did buy the IWC and really like it. I just got it back from having it serviced. I like a strap wider than 18mm to I notched a 22mm I had and added a deployent clasp.