You know, I’ve thought about that but the fact is that I go by taste/texture/appearance and I’ve used a wide variety of brands and never felt that I was not getting what I paid for. If it says San Marzano on the label and it’s from Italy (they take these regional designations seriously throughout Europe), I’ve never been disapoointed by what’s inside. I HAVE been disappointed–very disappointed–by so-called San Marzano’s grown in the US. These are in no way the same and, as I said above, I’ve found that the best substitute for Italian San Marzanos is not US "San Marzanos" but Trader Joe’s canned plum tomatoes.
All that said, the brand that I have mostly been using lately is Strianese, which does have the lable you are talking about, because they come in 14 oz cans which is perfect for making enough sauce for one person, i.e. ME. They are availabe online through Amazon.com.