A note that this content is separate from 2020’s “gigaleak“, and appears to have been simple happenstance. Forest of Illusion had released a near-final Ocarina of Time build version just hours earlier, and then came across the early beta content while dumping a different game.
The contents of these files are pretty incredible, beyond just looking cool. There are loads of elements that were originally planned for Link’s first 3D outing but were cut from the final game, with many being repurposed in later Zelda titles. Examples include the ability to rename your horse, the ability to complete dungeons in any order, and even the horse whistle.
At one point, the Sage’s Medallions were usable items, and it seems that the Shadow Medallion would have allowed Link to turn invisible for a period of time. The Fire Medallion would have enabled the use of Fire Magic (this was repurposed into Din’s Fire). There’s even icons for unused items that we’ve never seen before.
It’s important to note the importance of these discoveries. These beta files were thought to be forgotten; the prototype of F-Zero X was intended to have saved over this content on the cartridge. Not all of it was deleted, and now fans have an insight into how a legendary (pardon the phrasing) title came to be. Players have already gotten the old code running in emulators, allowing the community to run around in the early versions of the title that gave them so much excitement back in 1997.
Do be sure to check out the increasingly lengthy thread on Resetera, and check out the videos being uploaded to Youtube by user z64me, as there seems to be more footage going up as the day goes on.