Bottlecaps

Joe has a trash can full of bottlecaps behind the bar. He calls it his collection.
No corkboards or anything. Just a can full of bottlecaps.
“I just collect them,” he says, pulling another beer from the tap.
“From where?” I ask. “You just keep beer on tap, no bottles or cans. And you’ve never gone anywhere but up and down those stairs to your apartment.”
Joe looked at the trash can and scratched his head. “Beats me,” he said. “I guess this makes it valuable or something.”
He handed me the beer and tossed another cap into his collection.