His pot size bet certainly looks like he wanted to cut odds down to 2:1 to starve off a flush draw as well as being an attempt to win the pot right there. If he had a set, he could have re-raise you on the flop instead of just calling and peeling off the turn card. Turn looks like a blank - if I had a set and you checked into me, I think I'd go for just half a pot raise both to cut off the draw odds but still good enough odds to keep you in the hand for another pull on the river.

I think he has Ax - with x being mid-size or maybe even a 4. Did you ever find out?

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