Similar brackets were installed on the Boyd's Mill Pond Hydroelectric Works transmission line to feed loads near Laurens, SC. The caption describes a 33kV bracket, which is probably the one used on the line. The line also carries a pair of sidepins, but the insulator used has not been determined. The original insulator was an M-3065, and local collectors like me are trying to save an original set. Some sections of the line have modern insulators, but it is not certain that the line is still active. The generating facility is still generating power which is carried on 44 kV lines. This addition was likely around the 1930s, as the output lines have the traits of early Duke Power. Notice that the bracket in the picture has clamp pins. The "BMP" brackets have the metal at the ends flattened with holes drilled for a standard short-shank pin. Some of the pins installed are wooden with a metal shank.
Image courtesy of Google Books.