Now you know .....
The Zerk design, named after Oscar Zerk, used a fitting much smaller than the Alemite pin-type and did not lock the hose coupler or hand gun and fitting together.
Instead, the seal between them was maintained by the pressure of a pushing action when the operator applied the coupler to the fitting.
Oscar Zerkowitz. He was a brilliant inventor born May 16, 1878, in Vienna, capital of what was then the Austro-Hungarian Empire. His father, Bernhard Zerkowitz, was in the business of textile manufacturing, and the family had been prominent and respected since the time of the Holy Roman Empire.
Remarkably, the clever young Zerk was initially rejected from pursuing higher education, his appeals to the ministry of education were rebuffed, so he wrote directly to the Austrian Emperor Franz Josef with an appeal, got an audience, and impressed the Emperor, who then decreed that the young man be admitted to the college.
After graduation, Zerk relocated to England to study British textile manufacturing and to refine his automated loom. After four years abroad, he returned to Austria at age 27. It was then that the emerging automobile industry caught his eye.
Soon, he had designed both a six-cylinder engine and proposed a form of automatic transmission. Apparently impressed by reports of the steam cars of the White Motor Company, in 1907 Zerk arranged to visit the United States to study one firsthand.
He sailed for America aboard the RMS Lusitania, and it was during this voyage that he was inspired to improve the system of lubrication then in use on automobiles—grease cups and oilers.
Arthur Gulborg was a son of a co-owner of a small die-casting plant in Chicago. His job was to relubricate the die casting machines by refilling their oil cups several times a day.
This labor-intensive task led him to invent the grease gun (screw type) and grease fitting in 1916. He invented the fitting, a braided metal hose having a special end connection, and screw-type grease gun.
Gulborg and his father named it “The Alemite High-Pressure Lubricating System” after the Alemite Die Casting and Manufacturing Company where the idea was first formed.
In 1918, the Gulborgs approached the U.S. Army with this invention. Several test installations were made on white trucks in army service. Gulborg’s invention vastly simplified the task of lubricating army trucks. On July 10 of that year, it became standard equipment.
By 1922, Alemite introduced the “Button-Head” system to serve on a more rugged, heavy-duty lubricating system for many industrial applications.
The “Junior Button-Head” system was used to lubricate motorcycles and “Standard” and “Giant” versions of the button-heads were used in a wide range of industry including heavy construction equipment. The automobile industry, however, was the greatest immediate potential for sales.
Within five years of Gulborg’s patent, the passenger car became equipped with an Alemite hand grease gun and hose assembly. Grease guns became familiar to the general public, and most automobile lubrication was performed by the car owners. In 1924, the Allyne-Zerk Company of Cleveland, Ohio was purchased by Alemite, and the Zerk line of lubrication fittings and hand grease guns was added to the Alemite line.
This became known as a push-type system.
In 1930, Alemite introduced new hydraulic fittings. Today’s hydraulic fittings are very similar to the original version and remain the most popular grease application system in the world.
In 1924, Allyne-Zerk was purchased by Stewart-Warner, which also owned Alemite, a market leader in lubrication technology ("Alemite" actually became a verb meaning "to lubricate" for a while in the 1930s), and Zerk became a stockholder and consulting engineer.
In 1929, Zerk created a refined version of his lubrication nipple and assigned the patent to Alemite.
Zerk pulled back from business somewhat in 1939, moving from the hustle and bustle of Chicago to Kenosha, Wisconsin, where he heavily remodeled a mansion. He dubbed his new residence "Dunmovin" and resided there until his death in 1968, at which time, about 20 billion zerk fittings had been made
Oscar Zerk had invented leg slimming hosiery, quick freezing ice cube trays, fail safe brakes for trolley cars, and refrigerators for cars. He is also credited with designing and patenting stamped metal wheel covers (modern hub caps, not the coffee cup size original wagon type hub caps
Mower on and off isn't really that hard if you have two good arms and shoulders, but I don't fall into that category. 
