… There are references to recompression chambers earlier but it doesn't really say how they did it, if they did some sort of a schedule on air or not. Of course for history like that a library may be better than the internet.
There isn’t much in books either. Diving before the 1950s was virtually all using deep sea gear. There were a few sponge divers going deep and the very rare submarine rescue, but for the most part the work was less than 40'. The first decompression tables were developed more for caisson workers building bridges than divers.
The world’s navies paid for virtually all hyperbaric research but budgets were tiny because all their work was in harbors. Submarine disasters loosened up what little money was spent, and even then it was a low military priority. If it weren’t for a few powerful personalities willing to put their careers at risk it wouldn’t have been funded until decades later.
From what I could gather from divers ready to retire when I was in the Navy, early chambers were justified to treat omitted decompression more than what we would consider a treatment. Even then, the decompression probably resulted from entrapment than planned. Most were single lock chambers, and all were riveted. I understood that the “treatment” for DCS at the Experimental Diving Unit while they were developing/improving decompression tables mostly consisted of running them back down to their deepest stop and repeating or adding some time. You also have to remember that slide-rules were all they had to aid in the calculations.
As a result, there wasn’t much motivation to develop proper treatment tables until about the time that Oxygen was finally accepted in the late 1930s. Dräger’s system in 1917 never went anywhere because the war was nearing the end and money was needed to fight.
That is the same Dräger that we know today. I did some work with Dräger outside of Lübeck in the 1970s. There were photos of some of their early chambers on the wall but I couldn’t read any of the captions. If you are really interested you might get some insight from Gerhard Haux’s book Tauchtechnik Volume 1 & 2, Springer Verlag 1969. It deals mostly current Dräger products of the day but there might be some history buried in the text. Unfortunately, I don’t read German. Tons of photos and illustrations though.
You might be able to dig out some clues from Robert Davis’ book mentioned above. It is probably the best history of diving in that era available. You might be able to find a US Navy diving manual from 1924, 43, and 52 that might give you more insight as well. Of course the best library is at EDU in Panama City Florida. Please let us know what you learn.