This is the so-called Combat Edge model of the U. Air Force HGU-55P flight helmet with rear head pressurization system. The oxygen mask is the exclusive MBU-20/P. The present model was acquired via an American aviation-related Surplus Shop around 1998. The year of manufacture of the rear head pressurized airbag is 1991, and the year of manufacture of the interior thermoplastic liner is 1993, so I think it was used in those years and then released as a Surplus. The size of the shell is unknown as there is no manufacturing tag, but I think the shell is the same as the airbag with the LARGE size indicated on the airbag. The condition of the original helmet is as follows: both the interior and exterior of the helmet have reasonable signs of use and dirt, and there are some minor cracks on the edge rolls of the leather. However, it is not torn. The interior is complete with radio ear receivers and there are no missing parts including the wiring harnesses, but the ear pads are a little thin due to deterioration of the built-in sponges. The visor stopper on the top of the shell also shows signs of modification. 1991 is also an early model year for Combat Edge, and it is likely that this model was modified from the standard HGU-55P. The oxygen mask is dated 1994, which is correct for its age. The size is medium-narrow. Condition is generally good, the only thing missing is the exhaust valve cover on the right side of the body. That is the only item missing. This particular model is very rare among such Combat Edge models, as it was made in the very early stages of production and was actually used. The mannequin head in the photo is for photography and is not included in the product. We take note of serial numbers and images of evidence to prevent substitution. International Buyers – Please Note. Thank you for your understanding.