ASMU crampons - Mfg mark: "ASMU", size 41 - c.1950s - Note: In the ASMU catalogs it shows the round ASMU mark being used from the 1930s and newer. But the 1955 ASMU catalog shows illustrations of its products with only the "ASMU" letters being in the illustrations. The 1960s ASMU catalogs show the products having the round ASMU mfg mark.