You need to look at the company name on the primer packaging. If it is Union Metallic Cartridge Co. it is 1910 or earlier. Remington Arms-Union Metallic Cartridge Co. 1911 to 1916. Remington Arms - Union Metallic Cartridge Co., Inc. 1916 to 1920. Remington Arms Co., Inc. 1920 on. The earliest I see the UMC No. 2 primer is in the 1884 Union Metallic Cartridge Co. catalogue. The UMC No. 33 primer first appears in the 1910 catalogue. The UMC No. 2 and UMC No. 33 primers were still being offered in the 1923 Remington Arms Co., Inc. catalogue.
