Pea coats are cold-weather naval-issue garments. They were originally made using thick, coarse pilot cloth. This is the origin of the name of the coat. Pilot cloth became abbreviated to "P-cloth" and from there the coats themselves became known as "pea coats." Pea coats have become an enduring fashion item and many fashion clothing manufacturers have created coats based on the regulation pea coat design. If you want an authentic US Navy pea coat, there are certain things you should look for to assure yourself of a coat's authenticity.
Search for an authentic pea coat at a military surplus store. Fashion outlets are unlikely to carry authentic military supplied pea coats.
Check that the coat is double-breasted. Official navy pea coats are double-breasted to ensure warmth.
Look closely at the buttons. There should be six visible buttons and all should carry an anchor design on the front.
Check that the material used is 32 oz. Melton wool. Fashion replicas may use different fabrics to get a less coarse look than the authentic US Navy pea coat. Outside pocket openings should be a vertical slash, both left and right.
Ensure that the lining of the coat is quilted and that there is an inside pocket.
Look for a label proclaiming the coat to be an official US Navy coat. If you find such a label, you can rest assured that the coat is authentic military issue.
Sterlingwear's commercial copy "The Authentic" pea coat meets government specifications. Sterlingwear also has the current contract to supply the US Navy, meaning that even its commercial replicas are made to the authentic standards of those supplied to the navy. Another manufacturer making similar pea coats is Schott, which had a naval contract during World War II. Both Sterlingwear and Schott are based in the United States.
Color can be confusing. US navy color "Blue 3346" is such a dark navy blue as to appear black to the human eye.