Wow - look at the "meats" on the back of that Baby !
Any history on the photo ? Looks to be later than the "period", possibly when the truck was restored. The vanity "Lorne" isn't typical of 20's lettering.
Looking at this, it occurs to me that "upside down" steering wheel would be very inconvenient to drive, making you reach for the spark and throttle levers. Maybe fitted with a foot-feed ?
Photo looks like it is from the 60's or 70's to me. Do not recognize the manufacturer for this one. May be a local built rig or someones recreation from parts. You can obviously see the hose reel but I can't see any signs of a chemical tank in the bed. Hose size is too small for a pumper and no pump either.
Literature dealer Walter Miller is selling the photo on eBay - you can see it here - no additional details are provided.
Can't see anything that identifies it as a O.J. Childs rig but I can't say it isn't either. The cowl and seat design do not match any Childs rigs I am aware of at this point.