“It will probably be best,” said Thorndyke, “to say nothing about this coin, or, indeed, about anything else. We don’t want to enter into any explanations.”

“No,” I agreed. “It is best to keep one’s own counsel;” and with this we entered the hall, where Thorndyke led the way to a small door and pressed the electric bell-push. An attendant admitted us, and when we had signed our names in the visitors’ book, he ushered us into the keeper’s room. As we entered, a keen-faced, middle-aged man who was seated at a table inspected us over his spectacles, and, apparently recognizing Thorndyke, rose and held out his hand.

“Quite a long time since I have seen you,” he remarked after the preliminary greetings. “I wonder what your quest is this time.”

“It is a very simple one,” said Thorndyke. “I am going to ask if you can let me look at a Charles the Second guinea dated 1663.”

“Certainly I can,” was the reply, accompanied by an inquisitive glance at my friend. “It is not a rarity, you know.”

He crossed the room to a large cabinet, and having run his eye over the multitudinous labels, drew out a small, very shallow drawer. With this in his hand he returned, and picking a coin out of its circular pit, held it out to Thorndyke, who took it from him, holding it delicately by the edge. He looked at it attentively for a few moments, and then silently presented the obverse for my inspection. Naturally my eye at once sought the little elephant under the bust, and there it was; but there was no castle on its back.

“Is this the only type of guinea issued at that date?” Thorndyke asked.

“The only type,” was the reply. “This is the first issue of the guinea.”

“There was no variation or alternative form?”

“There was a form which had no elephant under the bust. Only those which were minted from African gold bore the elephant.”