A for Antique
It was a nice enough shop, John thought, and Sherlock seemed a tad interested too. A really, really small bit. Okay, he really wasn't interested. Something caught John's eye.
"Look at that vase. What do you think about getting that?"
Sherlock inspected it.
"It's ugly."
"It's an antique!" the store owner shouted, appearing behind them, "You've got to have an eye for these things."
"I do have an eye. And I can assure you that this 'antique' is at most one year old."
"How do you know that?" asked the store owner.
"I wouldn't expect you to know."
The store owner looked angry. John thought it was time to make amends.
"We'll take it!"