What structural feature is specifically mentioned as being characteristic of a trench coat's military lineage?

Answer

Shoulder epaulets

A trench coat often features double-breasted fronts, shoulder epaulets, and D-rings for attaching military gear, features not defining the original Mac.

What structural feature is specifically mentioned as being characteristic of a trench coat's military lineage?
inventionetymologyfabricapparelrainwear