Alf_flash, I am inferring from your last post that you may be feeling a bit put upon by all the comments, some more than a little sarcastic, about your watchmaker's lack of experience with this particular watch. Please be assured that every post has really been in sympathy with the best interests of you and your watch. A highly skilled watchmaker should find opening a case back to be totally elementary and, therefore, not in need of advice from a watch owner. So, questions have arisen in the minds of the posters about whether or not the watchmaker is up to the task. If, in fact, damage is done, you would be seriously unhappy. So, it is fair to expect that people are not interested in trolling you or your efforts, but that they will share best practices of their cumulative experience with you.