Denoting śaka era 605
"Until 1930, many scholars in the West believed that the zero was either a European or an Arab invention. A highly polemical academic argument was raging at the time, where British scholars, among them G. R. Kaye, who published much about it, mounted strong attacks against the hypothesis that the zero was an Indian invention. The oldest known zero at that time was indeed in India, at the Chatur-bujha temple in the city of Gwalior. But it was dated to the mid-ninth century, an era that coincided with the Arab Caliphate. Thus Kaye's claim that zero was invented in the West and came to India through Arab traders could not be defeated using the Gwalior zero.
"But then in 1931, the French archaeologist Georges Cœdès published an article (see reference below) that demolished Kaye's theory. In it, he proved definitively that the zero was an Eastern (and perhaps Cambodian, although he viewed Cambodia an "Indianized" civilization) invention. Cœdès based his argument on an amazing discovery. Early in the twentieth century, an inscription was discovered on a stone slab in the ruins of a seventh-century temple in a place called Sambor on Mekong, in Cambodia. Cœdès gave this inscription the identifier K-127. He was an expert philologist and translated the inscription from Old Khmer. It begins:
Chaka parigraha 605 pankami roc...
"Translated: The Chaka era has reached 605 on the fifth day of the waning moon...
:The zero in the number 605 is the earliest zero we have ever found. We know that the Chaka era began in AD 78, so the year of this inscription in our calendar is 605 + 78 = AD 683. Since this time predates the Arab empire, as well as the Gwalior zero, by two centuries, Cœdès was able to prove that the zero is, in fact, an Eastern invention. It is believed to have come to the West via Arab traders and was popularized in Europe through the work of Fibonacci (of the famous sequence of numbers), published in 1202.
"For a time, inscription K-127 was kept in the Cambodian National Museum in Phnom Penh. But during the Khmer Rouge reign of terror, while killing more than 1.7 million of their own people, Pol Pot and his henchmen also stole or destroyed close to 10,000 artifacts -- and this priceless inscription's whereabouts were unknown."
http://www.khmer-network.com/forum/viewthread.php?tid=9760
Not the earliest zero, rediscovered
How I Rediscovered the Oldest Zero in History
Numbers on a dial
The original zero
Cœdès, Georges, "A propos de l'origine des chiffres arabes," Bulletin of the School of Oriental Studies, University of London, Vol. 6, No. 2, 1931, pp. 323-328.
Diller, Anthony, "New Zeros and Old Khmer," The Mon-Khmer Studies Journal, Vol. 25, 1996, pp. 125-132.