Yes, that is sheet LI of the 1:10560 or 6 inch to the mile, which never has field numbers on. It is the 1:2500 or 25 inch to the mile which does but has not been scanned; these sheets are divided into 16 portions in 4 horizontal rows i.e. 1 - 4 top, 5 - 8 then 9 - 12 middle & 13 - 16 bottom.
ADDED:
And these are referred to as (say) LI.1 etc.