Form your description of the stamped numbers on the base L3451 could be an RAF Serial number, however I do not have a reference for aircraft histories by serial.
Checking Beaufort production, all were built with later serials, the prototype being L4441 and the first batch being L4441-L4518.
As far as I can tell almost all pacific Beauforts would have been of Australian manufacture and the serials would have been in the A9 series and would never have received RAF numbers. Some appear to have served for a brief period with 489 (NZ) squadron, mainly in Scotland.
The size may also be suspect, although I cannot find accurate info for the beaufort, most Hamilton/DH Hydromatic Props are aroung 10' diameter, giving a blade length of around 1700-1800 mm