The Broadbent - Bolton cephalometer was devised in:
The value of radiography as a diagnostic aid in orthodontics was proclaimed by W.A. Price in 1990, 5 years after the discovery of X-rays. 
The method of radiographic cephalometry was later derived from long-established anthropologic craniometrics studies and the use of the Broadbent-Bolton cephalometer devised in 1931. 
The head positioning cephalometer (more commonly referred to today as a cephalostat) allowed serial lateral skull radiographs to be obtained in a standardized manner, thus creating reproducible beam/ﬁlm/patient projection geometry. 
In turn, this standardization of radiographic projections allowed the precise measurement and comparison of oral and craniofacial structures, either directly on the radiograph, or through the use of superimposed tracings of bony anatomic landmarks obtained from the radiograph.

 
Ref: Jacobson 3rd ed page no 139
1930
1927
1931
1946