I don't know if it's exactly appropriate for this forum, but I would like to show you guys what happened to a lot of American gas masks after WW1.
As you may know, by the end of the war chemical protection development was moving forward very quickly, and many mask designs became outdated within a few years of their conception. This led to many masks being pushed onto the civilian market at low prices. Some, like the KTM masks, survived relatively intact, only having their military filters replaced with industrial ones. As you can see, the grey filtera were usually removed and replaced with ones more suitable for industrial usage. Instead of being in the bag mounted on the user's chest, the mask would have been held in a box, mounted on a wall, until it was needed. The straps leading off to the left of the industrial KTM shown are a harness to hold it onto the user's chest. The photo on the left is from gasmasklexikon.com, unfortunately the owner Johannes Moller passed away several years ago. On the right is my photo, although the mask shown was originally his.
In this next example, we can see the same process, except this time with an earlier Akron Tissot (AT) mask. Unfortunately, AT masks are very hard to find in any condition (even hard-as-a-brick, like mine) and there's not a lot of photos of them. The one on the left is owned by an old "friend" (the same one that sold me a fake Hypo). The one in the middle is actually mine, I believe it's old owner posted it on here once, and on the right is simply a period advertisement.
Some of the earlier masks, like the CEM and RFK designs, however, were not so lucky in being industrialized. Many of them were stripped down to their key components, namely the mouthpiece/flapper valve assembly and noseclips. This practice apparently carried on for many years, and saw some revisions, as we can tell from how the noseclips on the example mask to the left seem do not match the CEM design. It is also of interest that plastic versions of these mouthpiece kits have been found. (Once again, the mask on the left is from Mr. Moller's website.)
My final example is a strange one, and we're not entirely sure of it's actual origins. I'd like to ask your opinions on it's composure, and would be more than willing to provide additional photographs if needed. What it appears to be is a full-face mask from the mid 1920's that has parts salvaged from the CEM/RFK style masks. The hose, flapper valve and the black angled connection tube all bear a resemblance to military parts.
If you would like more photos of any of these masks, or have any questions/comments, I'd love to hear them. A lot of what I do is theoretical and I don't mind being contradicted.