It is a rarer byzantine Tetarteron after the coin reform of Alexius I, It was minted in Constantinople and it will have a small amount of silver ( about 3%). The coins from the city are much harder to find than the coins minted at other mints. I have three in my collection now ,I have been collecting them for about 15 years, they come to market only once or twice a year. I am new to this board but I specialize in this denomination.