...vehicularly speaking a Merc T1 van was, and I've just pulled that off, so let's see if luck is on my side!
Was outside the front door to my primary school (maybe even still is - but I ain't going to go wandering around there to find out in this day and age!). Roughly the size and shape of a 13W
One end of the fitting housed an 18W
I've never even seen this in a catalogue as far as I'm aware, never mind come across another in person.
Anyone got a clue?