"Yes, I'm sure it's a fake," Amy decided firmly. "If Mrs. Dillon bought this for the original Rembrandt she was cheated."
"Well, she deserved to be. She shouldn't have tried to buy stolen property."
"Let me look on the underside of the canvas," Amy suggested. "Sometimes that will give a clue as to the age of a painting."
They pulled the picture out from the wall and peered behind it. Directly in the center of the canvas was a strange, complicated symbol and beneath it the initials, "G. D." Both had been inscribed in India ink.
"What's that for?" Penny questioned.
"I wonder myself," Amy replied.
"Then it isn't customary to put symbols or initials on the back of a painting?"
"Decidedly not."
The girls studied the marking for a minute. They could make nothing of it.
"I can't explain the symbol," Amy said, "but I'm convinced this painting is a fraud."