Peacoat,
I'm pretty sure it was a 1938. Wish I knew where I saw it. Was one of those sites that you just come across when going through Google, etc. I think I'll enter 1938 US Navy peacoat and see what happens. To tell you the truth I'm not too crazy about the WWI coats. My favorite are the post WWII, and then the WWII coats. Supposed to go into the 90s today and tomorrow as it has for a good part of the summer. Maybe I'll take a cruise (or walk) in one of my coats (LOL).
At this link, you'll find the USCG uniform regs from 1930 as amended through mid 1941. On p. 94 of the .pdf, you will note an amendment dated 11/21/1938 replacing the prior specs for the peacoat (as recognized by the USCG) and substituting the specs as we know WW2-era peacoats to be.
https://www.uscg.mil/history/docs/uniforms/USCG1930UniformRegs.pdf
I am assuming the language replaced was the WW1-era peacoat specs. Since the USCG followed the USN uniform regs rather closely, with the exception of cap devices and gold buttons and corps distinctions, presumably the USN adopted these specs sometime around 1938 or before. Still a mystery to me is whether the 11/21/1938 amendment was playing catch up after a more prolonged period of USN specs being in place, or whether they came close in time to each other.