Certainly not a atmospheric diving system, but more a “time” marker. William S. Dunn and William F. Miller patented a shallow water helmet in 1916 with their patent US 1195793. The helmets were produced by the Miller Dunn Company from Miami Florida. The helmets were used by the Navy and by civilians for many years.
The shallow water helm patent can be found here: https://patentimages.storage.googleapis.com/ab/17/69/5e067cb0f68671/US1195793.pdf
If you want more information about these helmets please check: http://www.divingheritage.com/swmillerdunn.htm
Therebreathersite was founded by Jan Willem Bech in 1999. After a diving career of many years, he decided to start technical diving in 1999. He immediately noticed that at that time there was almost no website that contained the history of closed breathing systems. The start for the website led to a huge collection that offered about 1,300 pages of information until 2019. In 2019, a fresh start was made with the website now freely available online for everyone. Therebreathersite is a source of information for divers, researchers, technicians and students. I hope you enjoy browsing the content!