For those who might be interested, I received a response from the seller to my last query concerning the case back being original. Here it goes:
"Are you bipolar? First you accuse then you are sorry then accuse again. Ok here it is: NOBODY knows if the caseback is original to the watch or not, because UG doesn't even know this. I know this because I people still work ere.
Second that serial number does refer to a 1945 dated watch and SO DOES the other elements which I have explained to you. If that is the caseback or not, the material of the watch IS INDEED 18k gold -your main pain to the world it seems- why we know this? Because we checked the case with a metal denser -used to measure the micro plaque of metal plated objects- also the weight and the design. Now I am on a plane to Basel, and would love to keep chatting with you explaining the basics of vintage watches from UG but you simply insult and infer that people are dishonest. Does it show that on my 100% feedback? Sorry but you are WRONG AGAIN."
I have sent the following reply:
"Interesting. So your eBay description implies that the case back is original by relying on the serial number to date the watch. Then in your first response to me you flatly admit that "the case back is not original" and claim to have "stated' that in your eBay description, which you did not. Now your story is that no one knows (not even UG) if it is original or not? So which of these three things is true: (1) it is original, (2) it is not original, or (3) no way to know? You have alleged all three although your eBay description strongly implies only that the case back is original.
Can you cite any examples of an authentic solid 18kt gold Tri-Compax with a steel back and reference number beginning in "4"?
If I am crazy, as you contend, then please post all of our correspondence in the "Questions and Answers" section of your eBay listing. I am happy to have the public see how crazy I am and how reasonable and honest you are.
Also, you do not have 100% feedback.
Finally, my apology was conditional on you pointing out where in your eBay description you had informed buyers that the case back is not original. Since you have not pointed to any such statement that I missed, and in fact are now taking the different position that "nobody knows," you did not fulfill that condition precedent."