I've been practicing with a dremel tool for etching. I have a certain number etched onto different tools of my DH and mine. Not SSN#. You can use certain dates only backwards. DH had to chase down a skill saw that belonged to his father. He had description and serial number but I was practicing on it with an old dremel and etched a different number in a different spot. It ended up in a pawn shop. We got it back after 9 months. Never again did we loan anything out after that. It either never came back or if it came back, it needed to be repaired. We met the police at the pawn shop. Told DH to look for his mother's birthdate on it. There it was! Also had her initial in the middle and at the end of the date. Have used this method for other item's I always record it.