Blind plug to give you plain earth / ground connection - could be used for ESD mats, ESD bracelets, etc... In this case it was used to properly ground a cheap radio scanner's casing. The brass inlet was taken from a chead plug, the print was done using the Mendel I3 Berlin, 1.75mm PLA, 0.4mm layer and wall thickness, 12.5% squared infill - works a treat... But only in certain european countries, where they have real secure and rock solid electrical connections - sorry, Americans... You can't have it all! :-)