[Iron Munro]

Even back from my childhood, a “church key” was an opener for a can or bottle of beer. I never heard it used for anything else

That is my experience also, in and out of the Corps.

4" Church Key Can and Bottle Opener $0.39/Each

"This 4" V-Key can opener is nickel-plated. This standard can opener / punch is used to open small to medium sized cans, as well as remove bottle caps. This item is sometimes referred to as a church key."

[OftheOhio]

I am sure I picked up the term “church key” at Parris Island or infantry training at Camp Lejeune. That’s the first time I ever heard the term and you can bet we never had any bottle openers. I did hear them once or twice later referred to as John Waynes. Sure, if you go to the Wikipedia it says bottle/can opener, of course Wikipedia didn’t exist back then. Who knows what the Hollywood marines had though, for all I know they may have had feminine products in their kits too, LOL.