▁is ▁filled ▁with ▁arg on ▁( 9 9 . 5 %) ▁and ▁o xygen ▁( 0 . 5 %) ▁to ▁prevent ▁chemical ▁changes , ▁the ▁S hr oud ▁itself ▁is ▁kept ▁on ▁an ▁al umin um ▁support ▁sl iding ▁on ▁run ners ▁and ▁stored ▁flat ▁within ▁the ▁case . ▁ ▁Public ▁show ings ▁When ▁the ▁S hr oud ▁is ▁not ▁on ▁public ▁display , ▁the ▁case ▁is ▁closed ; ▁during ▁the ▁public ▁display ▁the ▁case ▁can ▁be ▁moved , ▁raised ▁and ▁opened . ▁During ▁the ▁last ▁centuries , ▁the ▁S hr oud ▁has ▁been ▁public ly ▁exhib ited ▁a ▁limited ▁number ▁of ▁times , ▁often ▁on ▁very ▁special ▁occasions . ▁▁▁ 1 8 th ▁century ▁▁ 4 ▁May ▁ 1 7 2 2 . ▁▁ 4 ▁May ▁ 1 7 3 7 : ▁to ▁celebr ate ▁the ▁marriage ▁of ▁Charles ▁Em manuel ▁III , ▁Duke ▁of ▁Sav oy ▁and ▁King ▁of ▁S ardin ia . ▁▁ 2 9 ▁June ▁ 1 7 5 0 : ▁to ▁celebr ate ▁the ▁marriage ▁of ▁Victor ▁Ama de us ▁III , ▁then ▁Prince ▁of ▁S ardin ia . ▁▁ 1 5 ▁October ▁ 1 7 7 5 : ▁to ▁celebr ate ▁the ▁ ▁marriage ▁of ▁Charles ▁Em manuel ▁IV , ▁then ▁Prince ▁of ▁S ardin ia . ▁▁▁ 1 9 th ▁century ▁▁ 2 0 ▁May ▁ 1 8 1 4 : ▁to ▁celebr ate ▁the ▁return ▁of ▁Victor ▁Em manuel ▁I , ▁King ▁of ▁S ardin ia , ▁to ▁Tur in . ▁▁ 2 1 ▁May