Yellowing serial number on a newish bag

this_is_rj

O.G.
Mar 1, 2011
475
531
Hoping a Chanel expert can shed some light on a serial number issue. Why do some of them turn yellow? I was looking at a bag today that was not that old, 2014, and it was in as new condition but the sticker had turned yellow. I have seen it in older bags, but never in a newish bag. Wondering if anyone knows why it happens please, and if and how it can be prevented? And if it means or does anything to the bag in general? Will this happen to all bags eventually? Thanks so much, any information on this is much appreciated.