Hi all,
I have just scaled from a couple of Pre-war Vincent works photos using the centers of fork spindles as a measure.
[For those sticklers for originality, some of these high-quality photos can be bought from a company called Stilltime.]
The top "PIP" is obscured by the tax disc holder, however estimating it's position, the result comes out really close to 15".
Unless someone out there has hard documentary evidence written or a pre-war detailed photo, [elusive things] I don't think it can be said for 100% certain which make of pump was fitted.
It would only be guessed at.
As Brian has said, they had a tendency to come adrift and bounce down the road, never to be seen again.
Regards,
Delboy.