The hulls. A bit more waterproofing. I don't have any Winchester Lacquered shells. Here is a comparison of a Lacquered Remington ARROW Express 12-gauge 3-inch Magnum and a regular Remington Nitro Express 10-gauge 2 7/8 inch shell, both from the late 1930s --
DSCN1332.JPG
and here is the box for the 12-gauge 3-inch shell --
Late 1930s Arrow Express.jpg