it looks like an Alexius I AE Tetarteron you can compare with examples from Wildwinds http://www.wildwinds.com/coins/byz/alexius_I/t.html
When anyone posts coins, they should include the diameter, unless the denomination and its size is well known. The size comparison with the finger in the picture helps, but not everyone would recognize this as a small coin. By the way, Victor nailed it.
Thanks for the clue. Closest i can find is this Manuel I http://www.dirtyoldbooks.com/gandinga/id/manuel1/man1014.jpg
It is SBCV-1954 John II JOHN II AE HALF TETARTERON S-1954 DOC 16 CLBC 3.4.5 OBV Full length figure of Christ standing on a dais, bearded and nimbate, wearing tunic and kolobion; holds Gospels in l. hand. REV. Bust of emperor wearing stemma, divitision and chlamys; holds in r. labrum headed scepter and in l. Globus cruciger. Size 15.59mm Weight 2.2gm