From verso of the card: "The left-hand panes in the picture are of a specially strengthened glass and the right-hand panes are of non-inflammable transparentcelluloid 1/10 in. thick, reinforced on the inside by 1/2 in. mesh wire netting. Both offer considerable resistance to blast pressure, although they may be penetrated by steel splinters from bombs. If this should occur, the holes and cracks in the damaged panes should at once be pasted over with stout paper to make the pane gas-proof. Additional protection is afforded by boarding up windows on the outside."