Hello Greg,
The article of -New's Detroit Museum director-Graham Beal-said- he was surprised at that high Est. $2-5 million--the museum had bought it in 1895 for $54 dollars

Two flags are known from this battle 1876 little big horn-the Lakota Sioux and North Cheyenne scoured the battle-ground looking for anything resembling a victory tribute,like flags and battle standards.
The Guidon in many respects the rarest of historic artifacts.
Sgt Ferdinand Culbertson found this under a body-3 days latter on burial detail.He was to give this flag to friends in Detroit area- the Fowel family abt 1880--Rose Fowel Reidel sold it to the museum for $54 dollars in 1895.
(the other surviving standard is much worse for wear, according to Beal)
The last word will be the highest bid--may not be from U.S.--open market,I guess---------------------------------Smithsonian?