When I removed the car’s headlining at the weekend I was intrigued to find a length of steel tube mounted in the roof at the edge of the windscreen on the driver’s side of the car. Investigating further, it’s clear that the tube goes through to the outside where it’s been blocked off (see photos below, first from the outside with the filled end of the tube zoomed in on, then from inside the car).
Could this be a mount for a 3rd windscreen wiper, as seen on some competition B20s, like the 1st Series car of ‘Ippocampo’ below?
And again here, on Chiron’s ’54 Monte Carlo Rally winner (which is, I think, a 2nd series car with a 2.5l engine):
Can’t resist a second shot of Chiron…
So here are the questions. Was this mount standard on a B20? Is it for a windscreen wiper? Might this have been a special order for a particular customer?
B20-2959 
This is perhaps already old hat. Nevertheless, my 3rd series B20 (Chassis no. 2500 – yes it is that number) does not have this tube fitted.