Back in the day, high brass indicated the quality of the shell, not necessarily a heavy load. Here from the 1915-16 Remington Arms - Union Metallic Cartridge Co. catalog one can see the wide range of 12-gauge loads from 2 1/2 drams pushing 1 ounce of shot to 3 1/2 drams pushing 1 1/4 ounce of shot available in their high brass ARROW shell --
Rem-UMC Arrow 12-gauge shells bulk 1915-16.jpg
All of those same loads were offered in the low brass NITRO CLUB shell except the 10A and 10F loads.