A brief survey of counting boards and abaci from ancient times to the present
www.ecb.torontomu.ca
THE EXCHEQUER
The “exchequer” derives is name from the chequered table which was used in England from c. 1100 for calculating expenditure and receipts.
Exchequer table

“The Exchequer is an oblong board measuring about 10 feet by 5...with a rim around it about four finger breadths in height, to prevent anything set on it from falling off. Over it is spread a cloth, bought in Easter term, with a special pattern, black, ruled with lines a foot, or a full span, apart. In the spaces between them are placed the counters, in their ranks.
The accountant sits in the middle of his side of the table, so that everybody can see him, and so that his hand can move freely at its work. In the lowest space on the right, he places the heap of the pence; in the second the shillings; in the third the pounds…As he reckons, he must put out the counters and state the numbers simultaneously, lest there should be a mistake in the number. When the sum demanded of the sheriff has been set out in heaps of counters, the payments made into the Treasury or otherwise are similarly set out in heaps underneath. The lower line is simply subtracted from the upper.”
—The Dialogue on the Exchequer, 1177.