Tracking personal copies of puzzles

I have a bunch of puzzles that I've modeled and printed for personal use. I want to track them in my collection, but I can't sell them, so I'd love a way to mark them as personal copies so they don't contribute to the collection's value. Originally, I thought hiding them from other users looking at my collection would be best, but for things like MPD Secret Santa, knowing which puzzles the other person owns/has solved is useful. That said, they probably shouldn't be eligible to be made available for sale/trade (not sure on the rules).