This was passed on to me from my father.
It is a Mask, Protective, Tank, M14A1 1961 Medium Size.
It is in good shape with dents and dings but fully intact.
I believe I found a little information about this item on the web.
I found one on the web for $75.00 but otherwise I haven't seen one of these listed on ebay before.
This listing is for the full set with the key as well (pictured below)
I am starting bidding at only 24.99 and have no reserve price set.
Good luck and happy bidding.
Gas Mask Website
US Army M14A1 Tank Mask
PRICE: $75 USD (plus shipping)
STATUS: 1 In Stock
The M14A1 (E56R2) (1960) mask included a nosecup capability; was constructed of black rubber (for low-temperature flexibility); and had smooth inner surfaces, better eye-lens adhesion, and improved eye-lens design. In 1961, atomic, biological, and chemical (ABC) protection was added to the nomenclature to make it ABC-M14A1.