On the bottom where it is standing might be a 5/ 16th whitworth threaded hole where a U shaped chrome bracket would be. You wind down the window of your car and wind it up to trap the clip over the glass and the twin flex which you plug into the cigar lighter. Made obsolete by a law stating you may park without lights in a 30 limit ( on the nearside of the road ) and on a road above 30 you need all sidelights on.
I´ve probably got one downstairs.
Keep posting, Wink