There are no frame or engine numbers in the RAF Norton spares book or any contract ink stamps,the only difference is on page 2 under note: PART No. 3605 K.S. CRANK RUBBER IS NOT FITTEDTO R.A.F. MODELS,the nearest other book to it is CONTRACT 294/C/5612 which has the same part numbers,prices & illustrations,the book probably dates from 1939/40.