Rare Model 129X Strobodelic Strobe Light manufactured by Chadwick-Helmuth, El Monte California. Tested and working, see video. 

I have been unable to find another model of this kind, and from the graphics I am estimating this was produced in the 1960s (the company was started in the mid-1950s and the Strobodelic patent was filed in 1967). Chadwick-Helmuth produced technological devices for the aviation industry, particularly helicopters, so I'm guessing  this strobe light was originally intended as a signaling device. 
Some very minor cosmetic wear but functions just fine. There is a flash rate control meter on the back. Dimensions 7 3/4 x 9 x 4 1/2 including handle.