It was a standard Lucas item about 2 1/2 " long for memory. It was stamped "LUCAS" and had a .015" feeler gauge attached. Also used on many British cars of the period.
Thanks chankly bore, I think you are correct.
I am being too subtle, I would like a reasonable res, in focus, cropped photo of a K30 Lucas screwdriver from a known original D series Vincent tool kit.
Here is a photo easily retrieved off web......but I find several types of these Lucas screwdrivers within a quick search.
Cheers
Craig