Ahhh - "white" folks took these photographs - you have to remember that while this gun leather MAY have belonged to him - it was not uncommon for the photographer to use "props" in his photographs - it was commonly done.
I collect WW I photos and I have two real photo postcards of different soldiers , both in sitting half views -both are holding an 1840 model "Old Wristbreaker" cavalry saber. The same phtographer took both photos. I have another which is a "full pose" of a soldier standing and he is holding a cap and ball Remington revolver. These items were basically Civil War "relics" that the photobgrapher had his subject hold - it made them look more "war like".
The photographers of the time period that you are looking at often carried "props" with them. These photographs were not made for the Chief or tribe - they were made for a variety of reasons. Some photographers wanted to honestly preserve history - others wanted to produce these photographs for sale to the masses back east who ate up this type of thing - they wanted to see the "savages" that were talked about in the newspapers and pulp fiction of the time. After reading and hearing about the Indians and their wars on the whites, etc. - they expected to see them with weapons and accouterments of war - that's what helped sell these photographs.
My response is not intended to affend anyone of Native American heritage. Let's face it - the whites broke every treaty that they ever made with the Native Americans. Some individuals and photographers were serious in their attempts to preserve the history and culture of the Native Americans through photographs, sketches, paintings, etc. They realized that those cultures were fast disappearing due to the genocide policy that was being undertaken at the time. Others saw it as a means to make money, something which the government and many of the general population of the time had no problems in doing at the expense of the various tribes.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63