In his welcoming speech, while addressing the European Meeting for Shoeprint/Toolmark Examiners, Sybrand van Hulst 1 comically stated

Criminal investigation would be much easier if every shoe had a number in its sole, in mirror writing… With every step the wearer would leave his number in the dirt, sand, blood, or grease… A bar code would be better still. A hand-held bar code scanner would be enough to determine who is the owner of size 13, printed next to the broken window.

Obviously this suggested method of identifying shoes is in jest and is not a realistic possibility.