This is a box of 9 Comfo Respirator felt screens. The box is original and initially held 10 felt screens. The felt screens are model BM-2101. The Comfo Respirator and the felt screens were made by Mine Safety Appliances Co. in Pittsburgh, PA. The side of the box has two patent numbers that date them to 1931-1932.. The back of the box has instructions for replacing the felt screens in the respirator. If you own a Comfo Respirator, these are the screens that you need. If you are a collector of mining accessories and equipment, this is something that you need!