Y6444 is a 1933 to 1935 frame. If you read the blurb on the Bonhams site you will see that they were advised that the frame on that bike is a later type. So the sprint special probably has the correct frame with the number transferred to the other bike.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.