It's a sole cleaner.
Whenever you accidentally step in chewing gum and can't clear it from a quick rub on the kerb, you take your shoes to Timpsons and they use one of these to pry the blob off the sole... Also works to remove tacks and staples that you forgot to sweep up off the workshop floor.
Larger versions were also available, with heavy iron fins on the back end, to make them more aerodynamic when thrown at cobbling apprentices... although I believe that practice has fallen out of favour, nowadays, so any such versions you find on Ebay will be well worth snapping up!!