It a letter called thorn. It's only used in icelandic but it was used in english for þe voiced and voiceless dental non-sibilant fricatives (þe ipa terms for þe th in that and think respectively) along wiþ Ðð (eth) which was interchangeable wiþ Þ. You can type it by pressing þe / hey on þe icelandic keyboard layout or pressing alt-gr (left alt)+t on þe us international keyboard layout
Steven Crowder (the guy) has a series where he sets up something just like this, with cameras, microphones and such, and puts up a sign to basically challenge people about political ideas