Kasumalai and our most famous Sami Dollar (Murugan dollar, Aaiyappan dollar) are probably effect of our trade with Rome. The last time I said something like this, there was big backlash asking for proof, so this post will have as much as proof you would want.
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Romans have traded directly with Tamil Nadu probably from around 500 BC (trade with Tamil Nadu could have been earlier through middlemen). We have found hoards of Roman coins across Tamil Nadu (Current Tamil Nadu and Kerala, some parts of Andhra as well). Literally every Sangam era excavation in Tamil Nadu has resulted in hordes of Roman coins. Proof of this that Madras museum has the largest collect of roman coins outside of Europe.
“The earliest Roman coins to reach India were the denarii or silver coins issued by the Roman Republic in the second-first centuries B.C. From the time of the Roman emperor Augustus (27 B.C. – 14 A.D.), the aurei or Roman gold coins also began to be exported to India. Many of the Roman gold and silver coins founded in India belong to the reign of Tiberius (14-37 A.D.). During the fourth-fifth centuries A.D., Roman copper coins were sent to specific trade-centres in South India and Sri Lanka.”
Roman gold coins were so easily accessible to Indians due to trade. Pepper, Pearl, Peacocks, bead ornaments, Gem, Sandal wood, silk, cotton, ivory were of value to Romans. They liked Indian goods so much that back home the Romans complained about money wasted in east for luxury products.
“Pliny’s Natural History, one of the principal Graeco-Roman works dealing with trade, notes: “India, China and the Arabian peninsula take one hundred million sesterces (an ancient Roman coin) from our empire per annum at a conservative estimate: that is what our luxuries and women cost us.” 
With so much easy accessibility of Roman gold coins, there were unintended effects in Tamil Nadu. People started punching holes in the coins and started wearing them as pendents.
[Gold coin of Justinian I (527-565 CE) – Image as reference to use of coins as pendents after punching hole through the coin]
Roman gold coing usually have Roman emperor in the front.
“The reverse display a themes that include princes and queens, gods and angels, public buildings, historical events, weapons and implements. Some of the deities on these coins are Peace-Nemesis, Jupiter, Minerva, Roma and Venus. “
Slowly these Gods were replaced by Indian Gods. If this looks to be far fetched theory, just see below, unlike a pendent which has designs only in the front our Sami dollars have design both in the front and back very similar to coins.
Initially the Roman gold coins were pierced and used. Then the blacksmiths have reworked to create pendants out of Roman coins. As it became popular through ages they imitated of the roman coin pendants.
[Roman coins imitated as pendents – excavated from Sri Lanka]
“A few of these coins were worn as pendants by the Indians. A large number of the imported coins were, however, melted for making new jewels. According to scholars, some of the foreign coins even served as currency in certain parts of south India. Coins in imitation of the Roman coins were also minted in India. Before using the Roman coins as currency, the Indians inscribed them with symbols and designs similar to those on ancient Indian coins. As South India did not produce coins during those days, the Roman gold coins were highly valued by the Indians.”
Later Blacksmiths reworked on these coins to make Kasu Malai. Now you know why we call it Kasu Malai. Reference to blacksmith working on the coins are available in Sangam literature. My first comic was based on this poem. So when I first read about the Kasu malai theory, I was immediately able relate to this poem where blacksmith works on a gold coin.
புது நாண் நுழைப்பான் நுதி மாண் வள் உகிர்ப்
பொலங் கல ஒரு காசு
Looking like gold coin held by the excellent strong finger nail
(of goldsmith) while inserting the tip into the sting to form a gold jewel
If you still don’t believe it, please see the image from Madras Museum special display of Kasu malai with Roman coins excavated in Sooryappatu. Such type of Roman gold kasu malai has been found in Tamil Nadu and Andhra.
[ Roman coins reworked as pendents for Kasu Malai – special display Madras Museum]
Kasu Malai design is not ingenious to India. On my research such design has existed in Italy as early as 7th century BC. Probably Indians have seen the ornaments on Roman traders and tried to imitate it with Roman coins.
[Gold necklaces from Camposcola Necropolis, Vulci. The top has 9 animal motif pendants, the other 7 discs of mythological scenes (Hephaistos forging Achilles’ helmet, Hippothéon suckled by a mare, Troillo slain by Achilles), mid-4th century BC, Museo Gregoriano Etrusco.]
The most important discovery could be the one below ,
“Another important piece of jewellery has been discovered from
Kampelayarn (Plare 16). The precise circumstances of rhe find remain a
mystery. The exact location of the site is also unknown but it may be
rentatively identified with a place called Kempupalayam, not too far
from Coimbatore ciry.39 This find is a unique circular Roman gold
pendant 4 em. in diameter and weighing 18.87 gms. The pendant has a
horizontally placed cylindrical loop at the top, and ir is made of two
sheets of gold, beaten thin and cut in a circular shape of equal size and
impressed .in repousse with designs; a legend has been engraved in
repousse on one of the sheets. The sheets, placed back to back, have
been soldered rogether by two narrow strips (tubes?) of gold which run
along the margins of the sheets. The solitary tiny hole near the edge of
the pendant may have been meant for pouring molten lac to fill the
interspace between the two sheets and to ensure that the repousse work
did not get obliterated due to rough handling of the object. A series of
around twenry tiny gold rings, two of which are missing to dare, have
been soldered at regular intervals, along the edge of the pendant. The
gold beads, recovered along with the pendant, were probably meant to
be grouped in the interstices between the rings and threaded through a
gold wire or chain such thar the pendant was laced with a chain of gold
beads. Portions of this wire or chain have also been found along with
the pendant.” 
So this is sure enough a proof that Indians tried to imitate Roman/Etruscan (Italy) pendent jewelry with Roman gold coins.
It could also have reverse effect with Roman jewelry having imitation coins in their own jewelry.
[Roman, Severan Necklace with imitation coin pendants, early 3rd century A.D. Gold – http://artmuseum.princeton.edu/collections/objects/41978%5D
On general note some of our gold jewelry could have had design borrowing from the Roman/Greeks. More and more I delve into trade in ancient Tamil Nadu, I just get to believe world was always globalized.
Chettinad region in Tamil Nadu still has stringed gold ornament jewel Kazhutooru , which they use it instead of Thali for marriage.
 SYMBOLS OF TRADE – Roman and Pseudo-Roman Objects found in India
CATALOGUE OF THE ROMAN AND BYZANTINE COINS IN THE MADRAS GOVERNMENT MUSEUM – T.G.Aravamuthan
https://docs.google.com/document/d/1EnoLAy1bKEITHsrWkSBMsJZEQL9nx32drsNUZ_7r5Bk/edit# [Compilation of all newspaper articles on Roman coins and trade]
Museum Catalog – MET, Berlin, Venice, Princeton Art