Original gas mask ARS 17 (Belgian issue?)
I only assume it is an ARS17, so a French made mask - but being that I came across it in Belgium (Ypres no less!) I would not be surprised for it to have been a Belgian issue. I don’t know what the TO stands for, or the red ‘I’ on the mask itself (in photos). I also do not know what the small hole in the bottom of the gas mask is for (ventilation? again, photos). Thankfully there is only minor damage from It (I assume) sitting in it’s canister for many many years, so the eyepieces have slighly come away from the mask material at the edges.
(ugh, sorry about the side ways photos, I should really try and fix that up)
Overall, I really like this piece!