Rather interesting orientation of the speedo drive. It does have the knurled knob for the rear stand and the long nut instead of the tommy bar for the rear flap hinge, which are correct for later C's. I know quite a few Shadows in that number range. I wonder which Mercury Crests it has. If it has "Vincent Engineers", they may be wrong, as that bike is likely to have been originally built in late 1952, based on the engine number. I have no idea whether or not the numerical part of frame number is correct, but it certainly raises a question (and I am ignoring the 'F' instead of an 'R' as typed in the description).