The advertisement featured a registration card that readers could fill out to receive a free trial copy of StuffIt Deluxe 16. MacFan42's eyes widened as he noticed a small print section at the bottom of the card, which mentioned a serial number: " STUFFIT- Deluxe-16-MAC- XXXXXXXX- AAAAAAAA". The asterisks hid the actual serial number, but MacFan42 suspected that this might be the key to unlocking the software.
StuffIt was the compression tool on classic Mac OS. Before ZIP became universal, Mac users shared .sit and .sitx files everywhere. StuffIt Deluxe 16 (released ~2015) was the last major version before the software faded into obscurity, replaced by built-in macOS Archive Utility and third-party tools like Keka and The Unarchiver. stuffit deluxe 16 serial number mac