http://www.racingvincent.co.uk/ who knows more than I do, this is his reply.
Thanks for sending me this, a very nice period photo (he refers to the photo in the previous post), taken at Brooklands from the Campbell circuit if I am not mistaken. The rider looks vaguely familiar but not really sure.
The photo is titled Beatrice Shilling 35, so I guess that is who it is and the date, but I suspect the bike is actually slightly earlier than that.
With the very early cammy Nortons it is actually a bit more difficult to identify the Inter's from Manx's as the differences were quite subtle but by about 34-35 the racing versions had become well established, with magnesium crankcases of a particular shape and layout.
The 'Manx Spec' tag was used pre-war (I have one myself), but in the early 1930's the early versions were not really coined Manx's, they were normally referred to as Racing Specification International's.
I would say this bike is one of these pre Manx racing Nortons. The tank is International from a road going model, but the main giveaway is the nut on the cambox cover, that shows it is an early racing cambox, with central oil feed. The gearbox has the early 'thatched roof' type gearchange cover, that indicates to me it is probably 32-33 in manufacture. I also have an idea that the crankcases look like magnesium, although they are of International pattern. However, this would be correct for the very first type of 'racing' crankcases, which were a sort of hybred of the Intnernational crankcase (that remained almost unchanged until the mid '50's) and the pure 'Manx' style SOHC racing magnesium crankcase that came in in about 34-35. I am currently importing a set of these very rare interim racing crankcases from Australia, although my set have many holes scattered around their circumference, where a conrod has made a bid for freedom!
Also of interest is the carburettor, which is downdraught but twin float, meaning it is probably on alchohol. Forks, front wheel and handlebars are all 'proper' for a genuine Brooklands bike, as is the exhaust, so I would think this is a genuine racing Norton, although due to its early date of manufacture, it probably would not have been regarded as a 'Manx spec' bike at that time.
I am pretty sure that Beatrice Shilling was one of the earliest female Brooklands enthusiasts, but I am not sure if this would have been her bike or one that she had 'loaned' for select events.
Regarding Paul's last comment; it is certain that it is her bike, she was a skilled engineer and quite capeable of maintaining and rebuilding a bike like this. As I mentioned in my last post, she built her own supercharger for the bike. She was at the forefront of motorcycle racing, a fact recognised by Norton who used her bike for publicity photos.
Many thanks to Paul for such a detailed explanation of Manx history.