Hi MissM,
Hope you are still awake/online when I finish this in case your next visit to Speke Hall is tomorrow.
Be sure to take a tape measure, or ruler to get measurments. I worked as a draftsman for 2 years prior to college, and during summers. I have seen a lot of graph paper, but none that has a 3x3 in a 5x5 grid. Maybe it is metric?
A brief search shows up lots of various grid sizes but nothing comparable.
I'd like to know smallest square size and we can extrapolate total size per card. Also, how many squares on the assumed 3 foot square linen? It appears to be 6, which would give a size per card of about 10 inches square.
Thanks,
Nick