If you are not cooking with San Marzano tomatoes, particularly when in-season tomatoes are not available, then you should start soon. But beware of impostors!
The president of the Cosorzio San Marzano says that at least 95% of the San Marzano tomatoes in America are not San Marzano.
How do you make sure they are?
First thing you do, you check the tin's label: it MUST say "Pomodoro San Marzano dell'Agro Sarnese Nocerino D.O.P."; it MUST have the symbol of the Consorzio; it MUST have the symbol of the DOP; it MUST have a "N° XXXXXXX", which is the Number assigned to the tin by the Consorzio.
But even if all of these apply, the President of the Consorzio says they have seen cases where labels were printed NOT in Italy, completely fake. Of course! Who is here in the USA to watch??? Very complicated!!! So, what do you do?
As always, best thing is to shop from a merchant you trust!!! And look at the price. If it is too good to be true, it is not.