So That's it!
Hello Brian and thank you so much for clarifying that for me .
You are right in that these Merlins were fitted to a Mosquito MK VI which crashed in 1948.
The A/C was built in1945 (airframe by Standard Motors Co. Ansty, Coventry and the Merlins by Ford Motor Co. Eccles Lancs).
I have had sight of the original Accidents Branch Investigators Report (Digital images from The National Archive at Kew) and "XXV" is how they typed it in that 1948 report. I have not had sight of the original AM Form 1180 (RAF Accident Card) but a recent e-mail from The Air Historical Branch (RAF) giving me the content of the relevant Accident Card uses the "XXV" designation also.
Was Nash Kelvinator a US company?
My thanks again to you, and the great resource that the 'Tech Log' is.
Ian BB