I don't believe anyone has mentioned the use of metal detectors at the Little Bighorn Battlefield site, where 62 volunteers were used. See Douglas D. Scott and Ricahrd A. Fox, Jr., 1987, <Archaeological Insights into the Custer Battle>, University of Oklahoma Press. No indication as to whether any of these were "amateur collectors" or not, though some were students at Sheridan Girls School so presumably were not. Jim Murphy [log in to unmask]