An old college friend of mine from 30+ years ago used to write his SSN on every college book he bought. He also used an engraver to etch his SSN into every tool he owned. The SSN was't all that important back then. I can't say when it became something of potential value.

Sadly he passes many years ago. His wife called me in desperation. She needed to get rid of and donate a bunch of tools and hardware filling their garage. However, everything had his SSN on it, I mean, he had an amazing collection of Snap-on tools with his SSN engraved on everything, down to the screwdrivers.

She trust me implicitly. We took everything out of their garage and donated it to our local high school's robotics club. The caveat was: The kids had to help me grind off the SSN from every single tool they got. That was an interesting week.