This one has me stumped. Case measures 27.7 mm (not including crown) by 25.3 mm (not including lugs).
Looks like you have a very nice Engineer 'I', missing the original band
Yep. Engineer "I". Here's a snippet of the 1964 ad Ken linked above.
Hi joebarkson, welcome back. I agree with my fellow panel members
Engineer I, a dandy one at that!