Condition, Condition, Condition is relation to military artifacts, especially World War One artifacts.
Also, is there any kind of artwork, name of soldier, or unit attributed??
In my collection I currently only have three WW1 US gas masks.
First,an undocumented complete set overall 80% condition with a very good condition mask, no cracks, or flaking etc...$150.00 value
Second, an 88th Infantry division, 313th Ammunition Train Co. D painted carrier complete set, in 80% condition, Excellent mask, clean filter, good hose $350.00 value
Third a 2nd Division, 2nd Engineers, 2nd Battalion, id'd set, in 70% condition, part of a 2nd ID group (uniform, painted Helmet, painted gas carrier), excellent condition mask, light crazing to lenses...$400.00 value by itself, the group is a $1500 set
There are too many variables to give you a good estimate of value with out seeing it.
Cheers