The Proof of the Pudding

"I'd be able to tell."

"Trust me. You wouldn't," the sales agent insisted. "Our copies are virtually identical to the original, down to a molecular level."

"Virtually..."

"There are always transcription errors, of course, but they're less than 0.002%, by total mass."

"Even biologicals?" the customer asked, "Isn't there a chance that the errors will corrupt the..." He frowned and peered at the glossy brochure, "...genome?"

"Our results are guaranteed."

"I'd still be able to tell," the customer stubbornly insisted.

"Really?" the agent asked, "Could you tell with me?"

"You're... a copy?"

The sales agent nodded.

"Where do I sign?"