Looks to me like it could be just about anything. You've shown almost no strength for the entire hand. Your incredibly weak turn bet after what looks like a useless 3 isn't going to scare him if he hit anything on that flop. He put in a 3/5 pot raise which could mean a queen, a jack, or just a total bluff if he senses weakness from you. Your check on the river just reaffirms that you feel weak and his $30 bet into a $50 pot is not an unreasonable value bet with a lot of hands worse than a set.