Most of these seem to have the serial numbers on the side of the block on a flat boss and number on the end of the crank shaft. 

Model L clearly cast in the hopper. Built from 1913-1915. 

Model LG  1916 the main bearings switch to grease instead of oil lubrication and are classified in the Power king line of engines. These also lost the embossed name in the hopper about the same time.  

6 hp - 6" Bore x 8" Stroke, 380 RPM, Flywheel diameter 34", 1200 lbs. 

10hp - 7 1/4" Bore x 9" Stroke, 380 Rpm, Flywheel Diameter 36", 1600 lbs.