Thanks Geoff, I thought so....eBay find (no one was watching) from a US seller. Good observation on the "waterproof". That detail got by me, you are correct. For the US market; post 1968 or 69, it would be marked "water resistant".
I'm on the same page as you regarding Swiss origin/production. The box pretty much clinches it and for me is the missing puzzle piece for the 30 jewel Ambassadors. High grade watches with no advertising in the US because they weren't available here?
My initial comment about perhaps breaking these out with a variant catagory was meant to maybe give the 30J Ambassadors a "place to live" because they really are unique to the line and up to this point have been a bit of a mystery.
There are currently 75 Ambassadors lumped into the no variant catagory, amongst them are 5 - 30 jewel models dated from 1965 to 1972, and there are 4 distinct designs not counting subject watch which makes 5 distinct out of 6. All 5 current (like subject watch) have the "1- xxxx" European style serial numbers with "Swiss" on face and 3 of those have the medallion caseback.
My point being possibly they should all be organized to aid in research, not to assign them a name without documentation. Perhaps a variant catagory under "Ambassador" like something as simple as "30" or "Swiss" instead of a letter? That way they would be together instead of lost in the "herd".
Just a thought.
Will add photos to the box thread as requested.