All five branches of the United States Armed Forces share the same officer insignia designs, but the regulations of the Navy, Marine Corps, and Coast Guard also specify the same dimensions for rank insignia to be on the collars of shirt and the shoulders of coats—the metal shoulder rank insignia worn by a 2nd Lieutenant in the Marines, for example, is identical in shape and size to the ones worn by Ensigns in the Navy and Coast Guard.
U.S. Navy regulations call for Ensigns to wear metal rank insignia on the shoulder straps of Blue All-Weather Coast, Blue Jackets, and Black Jackets. The insignia are centered on the shoulder straps, with the outer edge of the device three-quarters of an inch from the squared end of the strap, with the device oriented so that its long axis “points” forward and backward (fore and aft line). Coast Guard Ensigns wear shoulder rank insignia on the Windbreaker and Trench Coat in exactly the manner as Navy Ensigns, with the outer edge of the insignia three-quarters of an inch from the straight side of the coats’ epaulets.
Marine Corps 2nd Lieutenants wear shoulder grade insignia on both shoulder straps of Dress Jackets, Dress/Service Coats, the All-Weather Coat, Tanker Jacket, and Field Coat. All officers wear insignia centered between the front and rear edges of the shoulder straps, positioned so that the midpoint of the insignia’s outer edge is 3/4-inch from the armhole seam. A 2nd Lieutenant would wear the “butter bar” so that its long axis is at a right angle to the center of the shoulder strap.