An emoji that will not show in the Safari title bar

Found this in a Reddit thread this morning:

A locked (closed) padlock, with a key shown next to it.In the Apple artwork, the text on the key previously displayed UM242, which is an actual type of key.

This emoji does not show in the title bar of Safari, presumably to prevent less-reputable sites pretending to be secure (encrypted using HTTPS) when they are not.