From the January 1980 JFO Newsletter (by Don Bull):
But then I had an explanation from - where else? - Milwaukee, the beer capital of the world. It seems so authentic that all other theories may now be put aside. For one thing, Mr. J. R. Oberhofer, an old-time brewery worker, pointed out that the expression church key is much older than the device that leaves a triangular hole in beer cans. Indeed, it goes back to early days of the brewing business, when beer was first dispensed in bottles.
"The expression church key is old in the brewing business," he wrote. "I worked in a brewery for about 35 years and everybody carried a bottle opener or church key, perhaps so called because it looked like the top end of the kind of heavy ornate key used to unlock church doors."Mr. Oberhofer actually did send the cast iron bottle opener, and the evidence seems to me entirely persuasive. Thanks to him for settling a question that has puzzled me for many a year." (Editor's note from Don Bull) Thank you William and Mary Morris... I assume the reference is to a D Cast Iron Cap Lifter. Does anyone have any other theories on the origin of the term "Church Key"?
"I am enclosing an old relic that is about 50 years old. It's made of cast iron and from its weight and appearance, you can see its resemblance to a church door key. With the coming of cans in the brewing business, the bottle opener gave way to the can opener that makes the triangular marks - but the name church key was simply transferred to the new device."
From the October 1984 JFO Newsletter, Research by Joe Young our "Tin Can Opener Man" about Mr. J. R. Oberhofer is shared with us: Mr. Oberhofer, Sr. started at the A. Gettelman Brewing Company and returned there after Prohibition. He retired from Miller Brewing Company about 20 years ago [now meaning 1960's -ed.]. Gettelman was purchased by Miller in 1961. Mr. Oberhofer was a truck driver, and in later years, worked in the garage.
Circa 1900s Cast Iron Openers
Styles cited in the above article
D-1-21 Valley Brew / Stockton
D-3-23 Vals Favorite (Val Blatz Brewing Co)