Any advice on how to tell if a sport coat is a true three-roll-two lapel or a three-button jacket pressed differently for the picture on eBay? Certainly the button should be hidden, and I've read that characteristics of the roll itself can indicate full canvassing (thus a more natural roll without pressing). I don't really know what to look for, however. Your advice would be appreciated!
In addition to checking for the remnants of an old crease and the workmanship of the top buttonholes, you can also look at the pickstitching on the lapel. You will notice a difference on the right side (facing outwards for everyone to see) vs. the backside (facing inwards towards your body which no one can see). If the jacket was meant to be worn as a two button, the pickstitching will be noticeable outwards along the lapel all the way to the second button where it flips as the lapel flips so that it is still facing outwards along the edge of the jacket down all the way to the hem where the pickstitching usually ends.