This one is owned by Torsten Kunze in North Charleston, South Caroline, USA. It is on an early MGA, about 2000 cars into production in February 1956. Most likely an early vintage period aftermarket accessory. Kind of wide, it looks like it should be adjustable for width with telescopic tubing, but apparently not adjustable. There may be some trade nume underneath, but we were not going to remove it from the car to find out.