boiled leather
... that the German Army used pickelhaube helmets made of boiled leather until halfway through World War I?
... that the <a class="mw-redirect" href="./German_Army_(German_Empire)" id="mwA0E" rel="mw:WikiLink" title="German Army (German Empire)">German Army</a> used <a href="./Pickelhaube" id="mwA0I" rel="mw:WikiLink" title="Pickelhaube">pickelhaube</a> helmets made of <b id="mwA0M"><a href="./Boiled_leather" id="mwA0Q" rel="mw:WikiLink" title="Boiled leather">boiled leather</a></b> until halfway through World War I?