Here's a Link to Data regarding its body armor ratings, and other info:

[url]http://www.xs4all.nl/~gurth/pccs/bodyarmor.html[/url]

General Description:
M-1955 Armored Vest / USA / 1955
Basically, this vest is identical to the M-1951 but made from improved materials. It had one small breast pocket, and a useful rope ridge on the right shoulder, to prevent a weapon sling from slipping down. In the late 1960s, two large front pockets were added to many M-1955 vests.

-inuhbad