NEW (NOS) MSA M40A1/M40 Field Gas Respirator / Mask size: Small. Gas Mask is an authentic and original piece of militaria equipment manufactured by the MSA company in the United States. This mask is new, and has never been worn and has all of the subsequent upgrade features. Don’t miss the opportunity to own this unique and unique piece of protective gear. Filter cartridge and Outer Skin is. This gas mask was designed for military personnel and features silicone construction for comfort and flexibility. Represents a piece of. That holds historical and collectible value. In 1993, the M40 was updated and re-designated the M40A1. With production beginning in about January 1994. It has a new orinasal cup design made of a smoother silicone rubber. In the early 2000’s, the Army redesigned the outlet-valve and drinking tube coupler for the M40 series masks. It was found that the Outlet-Valve’s rubber composition could be upgraded. The upgraded outlet-valve was colored green for easy identification. The updated drinking tube coupler was similarly changed visually to aid in identification. The updated drinking tube coupler has two bands on the housing instead of one.