Jerry Slocum, a retired Aerospace executive, is a historian, collector and author specializing in the field of mechanical puzzles. His personal collection of over 40,000 mechanical puzzles is believed to be the world’s largest. It includes hundreds of puzzle padlocks including 34 Roman mask puzzle padlocks. He is the author of 16 earlier books on puzzles and their history including Puzzles Old and New in 1986, The 15 Puzzle, The Cube (about Rubik’s Cube), and The Tangram Book. In 2006, Slocum donated his entire puzzle collection and library of over 5,000 puzzle books to the Lilly Library at Indiana University, marking the first time a major collection of mechanical puzzles was made available to the public in an academic setting. He also founded The International Puzzle Collectors’ Party in 1978 that organizes annual gatherings in Asia, Europe and the USA of as many as 450 serious puzzle collectors from all over the world. Until his retirement in 2011.

Dic Sonneveld was an Information and Computer Technology (ICT) professional at Leiden University. Jerry knew him as designer of a type of mechanical puzzles, using partly self-written software. In 1997 Jerry asked him to contribute to the research for the history of the Chinese Puzzle, better known as Tangram (which was an international puzzle rage in the early 19th century). From that time on he assisted Jerry with literature research, library research and Internet research, which resulted in the 15 Puzzle Book (about the worldwide puzzle craze in 1880) and several others. All these experiences and knowledge now have culminated in the research for this book about Roman-Celtic mask puzzle padlocks. It all started in January 2013, as always, with Jerry’s simple question; he wanted to know more about these “ancient trick locks”.