Via [url=https://store.steampowered.com/oldnews/89760]the Steam store[/url]:

[quote=Valve]- Updated The Corpse Carrier
- Added the Holiday Restriction: Halloween / Full Moon
- Players who currently have this item will receive another random item from the Crimson Cache Collection
- The item has been moved from the Crimson Cache Collection to the list of possible bonus items received when opening a Crimson Cache Case[/quote]

Rumor has it:

- Those that receive random alternate items will see them as originating from Steam Support when a new items alert is acknowledged ("Customer Support Granted You:" in-game/"Support Granted" on backpack viewers)
- A pop-up message will also appear if you're affected. [url=https://www.reddit.com/r/tf2/comments/q6arvy/well_gamers_we_had_a_good_run/]See /u/Gamepro5's post on /r/tf2 for an example[/url]: [img]https://i.redd.it/2yga3r6b8xs71.jpg[/img]

- There is nothing to download as holiday restrictions are controllable through the item schema (specifically, by setting "holiday_restriction": "halloween_or_fullmoon")