Mid-Century TREASURE!

Hello... YESSS!!! My father-in-law just brought this to me this last Monday and I am so excited to have it! We own, and just opened up, an antique/gift/"junk" store and he has had this for about 20 years at his place, hiding in the weeds.
From what I understand this is a Fire Extinguisher from anytime from the mid '20's to the '50's (?). They were generally pulled by two people to wherever it was needed. These were used at train stations, large warehouses, airports/flightlines, anywhere where there might be large fires.
Aside from other research, I got a LOT of info from the new TV show "American Restoration" on the History Channel, starring Rick and his crew that does renovations for the "Pawn Stars" folks. I just happened to catch the episode "Pump it up" last Monday and this type of Fire extinguisher was the second item featured! He did a "little" renovation work and put it back in pristine condition: red, black, and shiny chrome! His was similar to all the others I've seen on here with the wheels approximately 24" apart. Hold on to your seat, folks! Rick bought just the tank only (no wheels, no nozzle/hose), at a junk yard for $20, got some wooden wheels instead of iron like a lot of ours seen on here, repainted it, got it "recharged" and re-loaded with 300 lbs. of baking soda, showed the customer it worked..., and sold it for $6800!
Bear with me here... Some of these extinguishers have a second, smaller, tank inside the top cap, about 7"X14"-18", that is pressurized up to nearly a 1000 psi. The kind on the show used a spike that is in the middle of the cap on top. To use, the tank that normally sits upright, is tilted backwards 'til the handle sits on the ground and one hits the end of the "spike" that juts out of the top of the cap with a hammer. This spike then perforates the smaller pressurized tank inside, pressurizing the entire 40 gallon cylinder, which then pushes out all of the baking soda stored in the tank. The interesting part is that the hose and nozzle are open (no way to turn off the nozzle!), therefore ALL of the baking soda is used with one puncture!
Another method used with these type of extinguishers (and I presume it MIGHT be the types with the screw-down knob on top) was that the larger cylinder contained baking soda and water (separated somehow?). When needed, the extinguisher was tipped over backwards and the screw-knob screwed down until it punctured/broke a glass cylinder inside, that contained sulfuric acid. The reaction this started created Carbon Dioxide quickly, which pressurized the main tank, therefore expelling all of the baking soda to put out a fire!
They (Rick and his crew) took the top cap off and found an inspection plate, and discovered that his tank had been inspected only once... in 1945!
I'm pretty interested to find out more about my "hand-drawn fire cart" because this is the only one I've seen with 40" between the wheels! I'll take the top off (kind of "frozen" on right now) and look for an inspection plate myself. I'll try to update later...