Vintage Ingenieur cases

As a begginer collector of vintage IWC Ingenieur models I want to learn about the cases. does anybody know if all Ingenieur cases had serial number on the sides? (meaning if not it means that it is not original case?)
Thank you!
Gal

The Ref 666 family of watches had a serial number stamped between the lugs at 6 o' clock. The Ref 866 watches from 1967 had the serial number on the back of the case.

For 866's the serial number may not be found on the outside but on the inside of the caseback.

I have observed that watches that goes through a factory renovation comes back with the number also on the outside, don't know if that has always been the practice.

/Anders

In the reference 1832 usually the serial number is affixed to the case-back during the revision.
Originally, the watch was not serial number available externally.
At least I have been able to ascertain.

regards