page 56 or not page 56 ?

i had a meeting in london last night so came back through paddington station. as you know i always look out for the giant posters which have page numbers, and i noticed that this one, page 56, also appeared without its page number.
i wondered if this was the missing link which would reveal the reason behind the sign page numbering ?
without
DSC01617.jpg
with
DSC01618.jpg