Staple! this year. The keychains are sequentially numbered from 1-150 and are black plastic with gold foil heat stamp. They will each come with an 'S' hook and ring attachment for your key(s). I'll also have these on my Etsy whenever I can get enough stuff together to get that cranked up.
To give credit where credit is due, I got the initial inspiration from A Continuous Lean.
(I would have posted an actual photo, but I was having a heck of a time shooting the foil. It's like a mirror)