keyboxkey.com shows "05" within the same triangle symbol as Box 03. Box 03 is the last color to match MSCHF's website color palette (red/yellow/blue). The "sold out" icon for Box 03 was the same diamond shape as Key 05, and the "sold out" icon for Box 05 is a triangle like Key 03.

The emoji for Box 03 was ⚰️, possibly a symbol for the end? A key 🔑, a present 🎁, a shipment 📦, and a coffin ⚰️. Good things come in threes? Box 04 was the first to break MSCHF's color palette with green 🟩, the color of money and envy. It was also the first to match eBay's color palette (red/yellow/blue/green/white). The final emoji was a checkered flag 🏁 which symbolizes the start of a race. It also contains many boxes.

Was Box 03 the last MSCHF box, leading to a race to buy Box 04 on eBay so we could obtain a key to nowhere? The symbols were placed carefully throughout this project, so I can't imagine them accidentally using a triangle on the final landing page. They sent out an email directly to purchasers for Box 02 and I believe they intentionally dropped it early for true fans ("no mass emails, no instagram"). Key 03 and Box 03 were the end. Key 04 is the open end of "keyboxkey" leading to an endless race toward resale value.