US M1 Liner 163rd Military Police Battalion

The 163rd Military Police Battalion (a historic unit originally formed within the District of Columbia Army National Guard from the WWII 121st Engineer Battalion) utilized M1 helmet liners typical of US Army MP units from the mid-to-late 20th century.

During the Vietnam era, the equipment of the US Military Police — including that of the 163rd Military Police Battalion (deployed as the "Capitol Guard" as part of the D.C. National Guard) — underwent several specific visual and material changes.

Characteristics of the Vietnam Era

• The Helmet Shell (Liner): During this period, the old compressed fiber liners from WWII were permanently phased out. Vietnam War-era helmet liners are made of laminated nylon (the P55 and P64 patterns). They feature an olive drab or orange/brown base color on the inside, but the outside was painted glossy black or dark green for MP use.
• "Capitol Guard" Markings: Specific to the 163rd during this period, the personal identification number "825" was often applied in white or contrasting letters on the side. This was sometimes combined with the characteristic red and white reflective MP bands running around or on the sides of the helmet.
• Interior Suspension: The internal webbing changed midway through the Vietnam War. Early Vietnam liners (up to approx. 1964) still used the P55 suspension system with intersecting straps tied together in the crown with a cord. From the P64 model onward, this was replaced by a stitched webbing system in an olive drab (OD) color.
• Production Codes (DSA): When checking an original helmet liner from this period, you will often find a contract number on the inside beginning with DSA (Defense Supply Agency), followed by the year (for example, DSA 100-73-C... for the year 1973).