Keep in mind that date represents the first commercial BC produced. Prior to that divers saw a need for some type of device to assist in controlling their bouancy, and many adopted the use of the old Mae West horse collar inflation devices almost 30 years before that first SP stab jacket hit the market. Cave divers experiemented as well during the 50's and 60's, using bleach bottles, Jerry cans (military type gas cans) and anything else that would reliably trap air and keep them out of the silt.