Double Striped Trowsers

The Dragoons wore these in 1839. 1st US Cavalry. NCO's wore two yellow stripes of 3/4" width down the outside of their pants leg.

These 1st US Cavalry pictures were recently brought to my attention, purportedly from Brandy Station in 1864:

Then in 1875 they resurface at Fort Robinson, Kansas. 3rd US Cavalry.:

June 25, 1876 Little Big Horn River battle, the trumpeter from Company A, Henry L Dose is Lt. Colonel Custer's Duty Orderly for the day. So instead of riding down into the Valley with Reno and A, G, M companies, Dose is with the command staff. His headless, shirtless body is identified by his mess mates and the double yellow trumpeter's stripes  on his trowsers.
 

In 1883, double stripes for musician's (trumpeters) are back in vogue and the regulations.