Additional source for ancient Greek and Roman history of the abacus
Additional materials on abacus history, addressing its Ancient Greek, and Roman origins:
Netz, Reviel (2002). Counter Culture: Towards a History of Greek Numeracy. History of Science, vol. 40, p.321-352. http://adsabs.harvard.edu/full/2002HisSc..40..321N (page 325 describes the Ancient Greek use of the abacus, including a third-century B.C. abacus found in Cyprus)
Ryerson, “A Brief History of the Abacus” http://www.ee.ryerson.ca/~elf/abacus/history.html (includes image and description of the Salamis Tablet dating from 300 BC.)
Salamis Tablet http://en.wikipedia.org/wiki/Salamis_Tablet
Stephenson, Steve, “Ancient Computers” page on the IEEE Global History Network http://www.ieeeghn.org/wiki/index.php/Ancient_Computers (Addresses the possibility that the abacus traveled from Rome to China via trade on the Silk Road)
Stephenson, Steve, “The Roman Hand Abacus” http://www.ee.ryerson.ca/~elf/abacus/roman-hand-abacus.html
Is there a strong enough connection between the milestone and the location of the plaque?