Birkenstock don't oil their "oiled leather" properly. I grew up oiling horseriding saddleware and Birkenstock's "oiled leather" is dry & hard, not supple & soft. I do it myself. These are "Franca"
Birkenstock Arizona Tobacco Brown Oiled Leather | END. (US)
Womens And Mens Birkenstock Arizona Habana Oiled Leather - Happyfeet.Com
Birkenstock Arizona tobacco oiled leather
Synthetic Birko-Flor vs Oiled Leather : r/Birkenstocks