Some, mostly modern (i.e. late-19C onwards) are for amusement. There are mass-produced ones, mostly now from India, and some up-market ones from Germany. There have also been some from Israel.
‘Puzzle lock’ was also a term applied to old combination locks, which in the distant past were mainly padlocks.
Some locks have included a puzzle element for added security. Some trick padlocks were simple catches that could be opened without a key, but looked like key locks.
There are collectors for all sorts. There are avid puzzlers who go for any or a particular variety of puzzle.
Other than combination padlocks, most are for amusement rather than practical use. UK government regards ‘antique’ as over 100 years; the antique trade rather prefers fifty years. There are several designs patented pre-1925, see HOFFMANN Puzzles old and new. Hoffmann is a pseudonymn, correctly, PROFESSOR HOFFMANN. The puzzle book is usually known just as Hoffmann.
Plenty of puzzle locks to be found on the Internet.
For the up-market ones, search for Popplock.
