Dynacorn International LLC is who makes the sheet metal that all the vendors sell.
I wouldn't say ALL. A fair number of parts I've gotten were Tri-Plus branded - Made in Tiawan.
Premier does Not get their 1947-1953 sheet metal from Dynacorn.... They get that from K.C. Smith Group in Phoenix AZ.
From your link: "KC SMITH GROUP INC
Distributor of classic restoration Chevrolet and GMC Truck parts and accessories for years 1939-present"
It doesn't say "Manufacturer"
I don't think Dynacorn does much manufacturing either. The get their stuff from overseas suppliers.
FWIW