This is the BEST advice!!!My only advice would be... don't be afraid to come home empty handed. Everything has to be perfect. The slightest doubt about some aspect of the experience will just grow in your mind. No need to rush the purchase.
It’s so easy to go on this mission and it would be such a great memory to get it on your trip. It’s easy to loose sight of the fact that you saved a looong time to get this and in the long term the most important thing is that you don’t regret the purchase because it’s not the one you want or have issues.
Check bags you buy extremely carefully especially those purchased from boutique due to strict and short number of days for exchange and returns.
In checking the bags I would check at least 2 side by side if possible. First looking at color which one is a deeper shade of black and surface which one has more even leather and no scratches etc.
Then for the one I think is better i would follow the stitching one by one through the entire bag paying attention to the stitching holes, if they were straight, any skipped stitches or anything weird (often times I find benign stuff like extra glue that can be easily rubbed off etc.)
Check the chain to see that it’s all as expected, the strap stitching and glue (the ends of the ML is glued vs stitched)
The hardware no scratches or uneven colors (eg chain color matches closure hardware color and not lighter vs darker gold etc)
The inside leather all gold no scratches not too loose and the serial sticker attached well, the serial number matches the one on the authenticity card
The inside flap zipper properly stored with the felt between the zipper pull and the underside of the flap so there is no major indentation from the pull left on the inside leather
The logo turn lock is centered and not crooked
Test the turn lock open close that it’s attacked well and not loose
Back outside pocket is centered and lined up right
Grommets where the chains come in/out of all looked good and centered proportionally to each other and to the edge of the bag (spacing wise) and there is no rusting on hardware