|This is from the original 100-Six Service Manual.|
The angle of the perspex is forward sloping like the later screens even though this is an early screen. In addition there are screws around the exterior of the frame which is not the case on the 'Longbridge' frames
Peter Svilans believes this was a very early variation which went out on the first 50 or so cars. A similar screen can be seen on photos of UOC 741, which was an early press demonstrator before becoming a works Rally car.