I just sold an E&J (Erickson & Johnstone) Resuscitator, one of the Lytport models.. In fact, it was exactly the same as they used in The Townsend Act of Emergency. I bought it from an old Civil Defense cache in Henry County, Illinois. I bought two new D cylinders for it, got new masks (the rubber part) made custom from a props shop in Southern California.. I had it inspected at a welding shop, since all the valves were made by Robert Shaw Co., they knew what to look for, as far as flaws or wear. I used it as my resuscitator and suction for seven years, it weighed about thirty-five pounds, so after I managed a hernia on a call, I stopped using it.
I'm one of those people that think old stuff is cool.. So I carried my personal EMT junk around in one of those wooden first aid boxes, and used the E&J box for all the oxygen needs. It's not like it didn't work either, it was great, just like any demand valve you would buy. I replaced the whole outfit with one of those Pro 3.0 pouches from Atwater Carey, nice little kit.
If you want a nice E&J, shoot for a Lytport 1. We used to have one in the firehouse on an old truck, it was under the hose bed, as if someone hid it there. (they probably did)