This M-1951 jacket was made under purchase order DSA 1-8297. We know this is an early Vietnam War designation, but we don't know how to read in that number the date when the order was issued.
The classic M-1951 field jacket was issued to the US Army for the first time during the Korean War, to be eventually replaced by the M-1965, better known as M-65.
That means that during the first years of the Vietnam conflict, the US Army, Special Forces, etc. wore the M-1951 in their combat operations.
The one we are selling here has a vintage patch of the famous 1st Cavalry Division, one of the most decorated units of the US Army, based in Fort Hood, Texas. They are a combined arms division, armor and mechanized infantry.
They started in Vietnam in 1965, transferred from Korea. The history of the division in Vietnam is rich and well known, and those interested can find many details in a number of easy to find sources on the web.
The patch on the jacket is subdued and made of twill. Those are difficult to find patches and have collectible value on their own. The owner of the jacket was a Specialist 5, as per sleeve patch.
This jacket is size Medium Regular. Actual measurements: 23" across the chest, pit to pit; 24" shoulder seam to edge of cuff; 19 1/2" underarm seam to edge of cuff; 18 1/2" ~ 19" shoulder to shoulder across the front of the jacket; 31" from collar seam to hem along the back.
The zipper is an old aluminum alloy, or alum, heavy duty Conmar in very good condition.