I notice some difference in the U1’s from watch to watch.
Notice the font used in the date wheel is different in the 2 watches pictured.
Also the # engravings on the bezel are much more finely detailed and smaller on the watch with the more detailed font. i.e. the 7 with the slight curve at the ends ( hope it comes out in the pics as I really need a macro function for these types of close ups)
Interestingly, the watch that has the finer bezel lettering and different date wheel ( unique in all the U1’s I have already bought and sold ) was purchased directly from the Sinn Factory – the paperwork is strictly Sinn , no authorized dealers name.