14 inches high agrees well with my own estimates. I did a crude analysis by resizing a full shot of William Sylvester to scale with the image above, and using his height as a guide I came up with the same measurement. 7 inches wide is a bit too narrow, though -- the sign's aspect ratio is closer to 2:3, which would yield a width of around 9 inches.
I doubt the original piece conformed to standard American paper sizes, since the production was based in England and the original graphic was almost certainly created as a photographic transparency. Still, 8.5x14 looks just about right, and with that size I'll be able to use an off-the-shelf illuminated menu holder as the basis for its display -- much less hassle than designing and building a custom backlit frame.
