Hi Graham, I've just spotted your post and also the one you posted on my original '1930's TT Memorabilia' posting.
I do indeed have HJ Bacon's TT 'crossbelt' number 34, white numbers on a red background, from I am certain, the 1931 Senior TT. My Nan used to work for the Bacon family at Great Hallingbury, near Bishops Stortford in Hertfordshire after the war. Bert gave the number to my Nan, who gave it to me when I was a boy in the 1960's. I'd love to have a chat with you sometime, I'll email you at the address you gave in your post.
Cheers,
Richard