Heavyweight wool pea coats have been sheltering sailors from the cold since the 18th century and can be a useful and stylish addition to a wardrobe. These coats originally were winter garments of British and Dutch sailors, and the name is Dutch in origin. The Dutch word "pij," for the type of wool used to make the coats, evolved into "pea." U.S. and British sailors wore these coats in World War II. Knowing what clues to look for can help you tell the general age of a vintage Navy pea coat.

Go through the inside of the vintage Navy pea coat, along the seams, to find a label. Labels may be inside the pockets, too. A black label with yellow letters signifies a pre-1965 coat. World War II U.S. pea coats will have a label that says, "Manufactured by Navy Clothing Factory," with images of anchors in two corners. These coats can be dated as having been made during World War II, between 1939 and 1945. No Navy pea coat will be older than the early 19th century, when the U.S. Navy began using them.

Examine the cut of the vintage Navy pea coat. Coats from the early 19th century were double-breasted and short. The British navy wore longer ones.

Look at the buttons. Early coats had three to six wood or brass buttons with Navy insignia such as anchors on them and may be dated as pre-20th century. British Navy coats had large brass buttons in the second part of the 19th century.

Determine what color the coat is. Vintage Navy pea coats are navy blue. U.S. Navy pea coats have been black since 1980.

Look for the telltale signs of modern fashion, such as lightweight fabric, bright colors, zippers or hoods. Such signs mean that your coat is not significantly old.