3.5 litre?
And there we have it. Another point to your total.
I obtained the puzzle from a 1970 magazine. It looks so much like an Alvis special the name of which escapes me, and also the Napier-Railton. There is no clue in the advert as to the build date so it could have been in period or an attempt ro recreate a late 30s racer.
Here's the original advert.
