The key - As there are ten cards, and ten lines on every card, the following ten are the first lines on the black side of each of them, viz

Originaltitel
Impenetrable secret
Författare
Horace Walpole
Språk
Engelska
Förlag År Ort Om boken ISBN
Printed for L. Donnelly; and A. M'Culloh, printer, at the Bible and Lamb without Temple-Bar, price 2s.6d. Where any purchaser, to whom this key is not satisfactory, may see the method, and be made perfect in the secret in five minutes, so as to discover the thonghts sic of another without the key 1780? England, London 1 sheet 4⁰.