I really don't know. Whatever line of them that Chef's Catalog sold about 10 years ago. I moved to this house and had a flat-top electric stove for the first time, and my old trusty copper bottom Revere Ware didn't work well on it. I needed something with a heavy, very flat bottom, and bang for the buck, the Sitram seemed to have the flattest (i.e., I was looking for maximum pan-to-burner surface) bottom. The pieces I would have bought separately were actually cheaper when bought in a full set. I've loved them. Learning to cook with both the different pans and the very different stove was a new juggling act which, if I do say so myself, I've perfected. My Revere just took a very short walk, my new (at the time) next door neighbor expressed an interest, as her pots and pans were a mish-mash of stuff picked up at auctions (her husband's hobby), her stove is gas, and she was happy to have them. I don't envy here the copper cleaning I did for most of my life!
Reading someone say that they're the best made me feel good! Hubby says he keeps seeing them on cooking shows where the kitchen is in European restaurants. It was just interesting to see that confirmed in this article.