I probably have its brother........ I have the bead type ring-clamp foresight from a side mounted .50 Browning MG from a Flying Fortress. Recovered when the crashed remains were dug up in the Fens in the late 80's. Together with an old wartime dated brass 3d and pre-war copper 1d (old english coins) that I have inset into the little wood plinth the sight now sits on.