The pot is a special pot that requires extremely high temperatures to heat. These high temperatures can only be achieved using special coal which new restaurants are not approved to use. Once heated, the pot retains the boiling hot temperature for the duration of the course. They use sake instead of water and this sake is essential. During the war and in post-war Japan, sake was not available so you had to buy a bottle of sake on the black market and bring it with you in order to be served.
After the suppon stew comes the ozoni. The ozoni is prepared by putting rice in the pot with the soup, breaking a few eggs and stirring. After the first servings are removed from the pot, there is a little left on the bottom. This heats and gets crispy and brown. This crispy rice/egg stuff is very good and is called okoge. You have to be very careful when scraping the okoge from the pot. The pot is fragile and VERY old. If you break a pot they get VERY mad. If you ever break two, you are banned from the restaurant.
I think it must have something to do with the pot, but the suppon at Daiichi is superior to any other suppon I have ever had and it is consistently great.