What's the noun for abacuses? Here's the word you're looking for.
abacus
(obsolete) A table or tray strewn with sand, anciently used for drawing, calculating, etc. [Attested from around 1350 (1387) until around 1470.]
A calculating table or frame; an instrument for performing arithmeticalcalculations by balls sliding on wires, or counters in grooves, the lowest line representing units, the second line, tens, etc. [First attested in the late 17th century.]
(architecture) The uppermost portion of the capital of a column, immediately under the architrave. [First attested in the mid 16th century.]
A board, tray, or table, divided into perforatedcompartments, for holding cups, bottles, or the like; a kind of cupboard, buffet, or sideboard. [First attested in the late 18th century.]