I have asked Thomann questions before and they have usually been good about answering, even if the answer is “don’t know”. In the meantime, you can see them both on Yamaha’s website. The descriptions are the same apart from the 402 having “Rottenburgh model” added to the end of the text. The only actual difference I can see is that the labium is a different shape: it’s longer and narrower on the Rottenburgh model, which should make some difference to the tone. There might be some bore differences but they are obviously not visible; the hole spacing etc looks the same to me.