I just bought this for $7.00 the other day. I don't know much about ancients, or this coin. The scans don't really show how nice this one is though.
Looks like Constantine the So-so. His son, Constantius the Average, didn't really do much of anything. [Everytime someone says 'the Great' I want to reply like that. Its about time I did!]
Its Constans, can you read the mintmark? (It should be on the reverse at the bottom of the coin) Look for something like CONSA or SMKA.
Like Arditarion said, it is Constans...I think the ex says SMKT, but can't tell, will try to do an RIC search later. Pretty good pickup for $7 stainless