Oldest is easy - my grandfather's Omega bumper. This was made in 1945 or 46 and given to him on July 31st 1947 (according to the inscription on the back).
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The newest is a bit more complicated as all my watches are now out of production, I just don't know when. I suspect it is my IWC 3717 Spitfire chrono which was made until 2011/2 (The successor 3777 was introduced along with new "triple date" range of IWC pilots at SIHH in 2012). I got it from AD in 2012 and it is now having it's 3-year service.
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