Yes sir it is, the pic is of a 1948 Rapide, just like the one I had a short ride on many years ago. I've always been enamored with Vincents and their lore, simply amazing machines and technically well ahead of their time. That experience was a dream come trueI take it your an HRD fan as well?
The Siamese marked Longbranch that I have is 1943 vintage, S/N 40L5736 and is marked in the same manor as the one above with the only difference's being: no serial number on the forend, typical LB "boot" safety and the letter "C" is stamped on top of the wrist.