Officers show their rank by wearing metal or embroidered insignia on their shoulders, collars, caps or sleeve cuffs. In addition, Navy and Coast Guard officers wear stripes of gold braid on their cuffs or shoulder marks, sometimes called shoulder boards. The insignia are fairly standard among the services and easy to recognize after a bit of instruction or study. It has not always been so. Over the years officers have shown their rank by such things as the number, size and pattern of buttons on their coats, sleeves or coattails; sashes worn across the chest or around the waist; the amount of gold, silver or other kinds of braid; cockades or plumes on hats; markings on saddle blankets; the cut and quality of uniform cloth; or by carrying a spontoon, a spear like instrument that was both a weapon and a mark of authority. In the early years of our military services the rank devices differed so much among the various Army corps and Navy units that it was difficult for service members of one activity to recognize the ranks of another activity.
From: Why is the Colonel Called "Kernal"? The Origin of the Ranks and Rank Insignia Now Used by the United States Armed Forces
Information borrowed Naval Historical Center
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