A Guide to Figuring out the Age of an Undated World Map by https://xkcd.com/1688/
Map Age Guide

xkcd
@infobeautiful Have to add to the caveats that not all map publishers updated and corrected errors at the same pace. Some were amazing for U.S., but terrible for Africa. There was no standard objective source for changes and latest information that you could reference, everyone was scrambling. That being said, Randall Munroe is just so great. And his videos are awesome. Love to watch how he thinks.

@oldmapgallery @infobeautiful

I’m a proud resident of “Danger: Radioactive Exclusion Zone! Avoid!”

@infobeautiful
This is the greatest XKCD. We used it to date our undated terrestrial globe ("1952-1953").
@violanders
It would be just great if someone gathered a collection of maps representing every end point on this chart.
@infobeautiful
@mountdiscovery @infobeautiful ooh that looks cool

not sure what to do with that though. Maybe in the future I'll have an obsession with maps?