Id bet not too many here under age 40 have ever heard of a church key.
There were pull-tab pop-tops in the early '70s - maybe earlier. By the late '70s, the "stay-tab" took over.
IIRC, there is (or was) a craft brewery in the northwest that's using flat-top cans again. Maybe the cans are cheaper without the captive pop-tops. It'd be interesting if it came full-circle.
Is it me, or is the trend in craft brewing to put the beer in cans?
High end canned beer seems to have exploded in the last 18 months.