in the late s by doubts and differences of opinion over which caliber to adopt. french anti-aircraft weaponry was lacking in ; the french had rejected a mm design by hotchkiss in but reversed course when schneider could not finish development of a mm gun in time. in, boys, commonly known as the "boys...
. in , snell b was introduced, the first widely adopted standard for bicycle helmets; this has subsequently been refined into b and b (see standards below). at this time helmets were almost all either hard-shell or no-shell (perhaps with a vacuum-formed plastic cover). ventilation was still minimal due...