Like the double-sided wafer lock, the single-sided wafer lock had its actual beginnings in the 1860s, but the manufacturing process was not cost effective and it had competed with the pin-tumbler lock for the same market. Research indicates that it was Briggs & Stratton who re-introduced this type lock which appears to have been first used in 1924 automobiles.
A Perfect Fit for the Auto Market
The single-sided wafer lock was Briggs & Stratton's answer to the pin-tumbler lock. Like the pin-tumbler lock, it used distinct depths and spaces and could accomodate many more key changes than the double-sided lock. Because it was inexpensive to manufacture it found its niche in the automobile industry between the cheap pseudo locks of the electric companies and the more expensive pin-tumbler locks.
A Revolution in the 1930s
By the late 1920s Underwriters Laboratories had pointed out security issues with automobile locks. Single-sided wafer locks underwent various transitions in the early 1930s in the search for additional security. In 1935 Briggs & Stratton introduced the side-bar lock which became their standard for the next five decades.