This link was shared with me: https://www.mediawiki.org/w/index.php?title=User:Quiddity_(WMF)/sandbox&action=edit&oldid=2607307
However when I follow it, I see the current revision of that page. In order to go to the right revision, it needs veaction=editsource: https://www.mediawiki.org/w/index.php?title=User:Quiddity_(WMF)/sandbox&oldid=2607307&veaction=editsource
Not sure if this is expected behaviour?
Also discussed at https://www.mediawiki.org/wiki/Topic:U1d8xavtqmu1wgv9