"The flange focal distance of a lens is the distance from the rear surface of the lens shutter (i.e. the front surface of the lensboard) to the focal plane (i.e. the film plane) when the lens is focused at infinity."
I always assumed the flange focal distance was pretty close to the indicated focal length, exept of course for telephotos.
Go not to the elves for counsel, for they will say both yes and no.