I keep it in my wallet now.
A brief story from 2008:
I was sitting in Union Square, idly eating lunch with a group of about six other people, when a young man suddenly approached me.
“Excuse me,” he said. “Are you Jewish?”
“No,” I replied, truthfully.
“Oh,” he said, disappointed but not disheartened; he had a plan for just such a scenario. “Here’s a picture of a smiling Rabbi.”
“Ah,” I said. “Thank you.”
He smiled. “Have a great day,” he said.
And then he was gone.