Some time back I suggested you could tell which males were emerging and which weren’t by whether or not you see a belt. If there was a belt visible, shirt tucked in, etc., emerging was a stretch. We found another device to figure which countries our fellow tourists were from.
Shoes. Shoes tell the story. No kidding. We would look at shoes, guess in our minds where the folks were from, and if we could get close enough to hear them talk, decide if we were right or not. By and large, we got this one right.

Germans (with Austrians included — it would take some time to hear that great oesterreichischer “klingt wie ein Lied” accent), for instance, are the most noticeable. They wear heavy boots, grey thick socks, and they often had walking sticks.
Italians — well, they are obvious (besides the locals). Hair, clothing, but their shoes are thin and fashionable. Anything more stereotypical than that? Even their tennis shoes were noticeable.
Americans — they wear Nikes or cross-training tennis shoes. And they look lost or they are looking at Rick Steve’s book on Italy. I’m guessing we saw 500 of those books during this trip.