General Order No. 286 (Fall 1864) formally authorized officers to ditch full straps and epaulettes in the field. Instead, "marks of rank" could be worn directly on the shoulder or coat—simpler, lower?profile insignia like pin?on bars or stars

WAR DEPARTMENT,
ADJUTANT GENERAL'S OFFICE
WASHINGTON DC, Nov. 22, 1864.

Officers serving in the field are permitted to dispense with shoulder-straps and the prescribed insignia of rank on their horse equipements. The marks of rank prescribed to be worn on the shoulder-straps will be worn on the shoulder in place of the strap. Officers are also permitted to wear overcoats of the same color and shape as those of the enlisted men of their command. No ornaments will be required on the overcoats, hats, or forage caps; nor will sashes or epaulettes be required.

By order of the Secretary of War;
E. D. TOWNSEND
Assistant Adjutant General

The individual junior officer rank pips from the Smith patent rank set. Often seen in pictures, A set of 8 for all junior officer ranks.