I had shared my album of post budget Pondy Bazaar with the IIMA- Chennai group. One of the alumni Mr Srikant pointed out that this Pillayar has a Shanku and Chakram, normally associated with Vishnu. Only after his response, I noticed this uniqueness.
I have no idea about how Pillayar came to have the Sangu and chakram, but I am aware that the masons and sculptors of gopurams take liberties with the terracotta or stucco figures that go on the gopuram, often deviating from the accepted norms of iconography. If anybody has any other explanation, please do share it with the readers of this blog.