I appreciate the thorough response and I expected that analogy. I wish I were still in college where I had access to an electron microscope; I could pop a coin inside and zoom in nice and close on the raised lettering.
In reality, it's probably a mixture of both. The harder, more abrasive environments of streets, vending machines, and dirty pockets make more scientific sense to me. However, I have been pulling some late nights for work this week and am not thinking as clearly as I prefer!