sure looks like a seam, at least in those 2 tubes...still possible you might have real 531 in the others. It's pretty common to see big volume builders sub a cheaper head tube, and those are often seamed...but when one of the main 3 is seamed I'd say you can't trust that any of the others will be 531 (butted or plain gauge) which should always be seamless. Not sure about the (rare) Reynolds "A" tubing, that was a light and good quality tube but not sure whether cold-drawn and seamless (though I had assumed it was).