This vintage chesterfield overcoat was made by Brooks Brothers in the 1960s (between mid 1962 and 1968). The styling is straight out of the early 1930s, with lazy peak lapels, conservative dimensions and a fly front. If the union label wasn’t there, I would swear it was made decades earlier.
Chest (pit to pit): 23″ (doubled = 46″)
Shoulder to shoulder: 18″
Sleeve (shoulder to cuff): 25-1/4″