Hi Longines lovers Apologies if that question has already been addressed elsewhere. When browsing through vintage Longines I appreciate Longines' practice of stamping or engraving the matching case number on the case back as well as on one of the lugs. Great way to check and avoid Frankongines. Unfortunately, I noticed that Longines stopped that practice at some point, some time in the 60s? I'm interested in knowing when Longines started and stopped this practices. Also tried Dr. Google, but in vain. Many thanks for sharing your insights.