From the Hindu:

A Chera coin made of silver, with the portrait of a Cheraking wearing a Roman-type bristled-crown helmet, acquired by R. Krishnamurthy, has come into focus for its potential significance. Dr. Krishnamurthy is the Editor of Dinamalar, a Tamil daily.

While the portrait is found on the obverse side of the coin, its reverse shows traces of "bow and arrow," the symbol of the Chera dynasty. The coin is highly corroded but the portrait is clearly visible. It has a diameter of 1.6 cm and weighs 1.8 gm.

Dr. Krishnamurthy procured it a year ago from a coin collector named Veeramani who belongs to Krishnagiri in Dharmapuri district in Tamil Nadu. Mr. Veeramani was said to have obtained it from a gold-panner working on the sands of the Amaravathi riverbed in Karur.

The obverse side of the coin has the portrait of a king, facing left, wearing a Roman-type helmet. With a flat nose and protruding lips, he has a wide and thick ear lobe but wears no ear-ring. The person depicted appears to be elderly.

There is no legend above or around the portrait. There are traces of "bow and arrow," the symbol of the Chera dynasty, on the reverse.

Dr. Krishnamurthy, a numismatist of repute, said: "Probably this coin is an important discovery. The importance is due to the portrait, which may represent a Chera king.

Unlike other Chera silver portrait coins, the king's portrait on this coin faces left."

Earlier, several Sangam Age Chera coins including one with a portrait and the legend "Mak-kotai" and another with the legend "Kuttuvan Kotai" had come to light. These were discovered from the Amaravathi riverbed.

The coin in Dr. Krishnamurthy's possession is more or less similar to these two, which have a portrait with a legend above it. The reverse side is blank.The latest coin points to Romans having had trade contacts with the Chera kings.

Dr. Krishnamurthy said: "There are so many proofs to show that the Romans had trade contacts with the Tamils, especially with the Chera country. From the later part of the first century B.C. there was a big trade contact between Romans and the Chera kings. This [coin] clearly establishes that the Roman soldiers had landed in the Chera country to give protection to the Roman traders who had come there to buy materials. A Chera king with a Roman helmet is important. This especially has bristles."

Dr. Krishnamurthy added: "Praetorian guards wore helmets with bristles.It was generally believed that the Satavahanas were the first indigenous monarchs to issue silver portrait coins. That has been disprovedby the discovery of Mak-kotai and Kuttuvan-Kotai coins belonging to the first century A.D. or a little later. But the coin under consideration may beearlier to the previous portrait coins already published. This coin maybelong to the first century B.C. and may be earlier to Mak-kotai andKuttuvan-Kotai coins."

Silver coins issued by Augustus and Tiberius, the Roman emperors, have over a period of time been discovered in large numbers from the Coimbatore-Karur tract which formed part of the ancient Chera country.

... a photo of the coin (the image rather like that of a mohawked punk rocker, actually) accompanies the original article ... obviously there's a bit of anachronism if we're trying to get praetorian guards connected with this coin if it is B.C. (maybe not?) ...