I need a little help with an ancient Greek coin......

The 2x2 that this has lived in for 45 years is marked 'Byzance' tetra-obol, 4th Cent. BC.
It weighs 2.4 grams and is 13 millimeters in diameter.
Is it a obol or a tetra obol.
Any ideas as to value ?
Thanks for the help !!
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Comments
The denomination is usually spelled "tetrobol", and the city is usually spelled "Byzantion" or Romanized to "Byzantium" - the city which would eventually become re-made as Constantinople, now Istanbul.
If you Google "Byzantion tetrobol", you'll find a whole bunch of people selling similar coins. Most seem to be in the $50 to $100 price range?
Roman emperor Marcus Aurelius, "Meditations"
Apparently I have been awarded the DPOTD twice.
Thank you for the great help !
I appreciate that......