As an army doctor, Henry would be a commissioned officer, and accordingly, the online biography which Jane finds of him states that he was given the rank of captain (rank insignia of three diamond-shaped pips in a straight line on the epaulets). But when we see him, he wears the enlisted rank insignia of a corporal (two stripes on his upper sleeves).
The French waitress uses the term"Brits" which is a modern Americanism and Henry,in addition to the gaffes already mentioned regarding his uniform,is clearly wearing German ammunition pouches on his belt.