I broke What3Words
Riffing off telenaut's post and this image of the map overlay he uploaded, I tried out words legible on the map tube that "entries" could reference. "Secret" and "map", both singular and plural, didn't lead anywhere. But "treasure" is interesting. See what happens when you type "wells.barns.treasure" into What3Words. Zoom out A LOT. Has DRM been trolling us this whole time?
Try it out before you read the spoilers below:
>!This leads to coordinates -85.2053550, 46.1881460, which is at the absolute bottom of the What3Words map, and the Google Map, and the Bing Map, etc. It's near the south pole in Antartica. Once you click another square in What3Words, it's impossible to find the wells.barns.treasure again by clicking. You have to enter it in again. You can pull it up in Google Earth to see its proximity to the south pole. !<