Not sure if it's easy to tell but one of my Birks is a completely different colour to the other pair.. the right one is more orangey & textured whereas the left
Why Are My Birkenstocks Turning Black - How to Clean Them
Bunny Delft & Custom Art Birkenstock — Akiko Tsuji
The Birkenstock Buyer's Guide | Sizing, Fit & Care | allsole