For sale here is a classic US Naval peacoat in the post WW2 style although we're not great at dating these as they remained very similar for a long time. I'd guess 60's/ 70's for this one but could be wrong.
Sleeve - 24.5
Shoulder - 18
Length ( including collar ) - 32
Armpit to armpit - 20.5
Fit - labelled 40 short, they're fairly trim though and weren't intended to be worn over a jacket.