Edgar Wallace,
The Law of the Four Just Men — The Man Who Was Acquitted
(1921)
“ The underside of the palm had evidently been specially prepared for the silk came off easily, leaving a thin grey slab of slate-coloured clay in the centre of which was clearly the impression of a key."The little hole at the side is where you dug the point of the key to get the diameter?" said Manfred, and Leon nodded."This is the master key of Baxeter Gaol, my dear Manfred," he said with a smile, as he laid it upon the table. "With this I could walk in—no, I couldn't." He stopped suddenly and bit his lip."You are colossal," said Manfred admiringly. ”
