If you bought your copy of Aperture Inspector prior to November 2013, your serial number was sent to you by email when you purchased it. Every Aperture Inspector serial number starts with “INFOSTILL”. Chances are if you search your inbox for that, you’ll find it. If not, please use the Contact page to request support.

If you bought yours more recently, then check under “My Downloads” in the Me menu. You'll find your serial number listed next to your purchased product.