Hi Hanno,
I was quite surprised as well when I saw it, the picture was originally posted years ago by Cletrac in a long thread on the Motley mounts. It was published in the William Gregg Profiles book in the section other anti aircraft weapons on the LAAT page and the caption is as previously mentioned.
I'm not sure when this MK of mount dates from or what MK it is, unlike most of the other types it does not have the counterbalancing springs.
I have taken another shot of the picture so hopefully its better and also put on another picture of the same mount but mounted on an unknown truck.
James
