A Hagelein spy camera sold for $17,677 in an auction of cameras at Bonhams Hong Kong on December 3.
It's an 1894 American copy of an earlier British watch camera. It worked by inserting a small slide and pressing a button on the side.
It could then be folded back up into a mock pocket watch after use.
A contemporary review of the camera in Anthony's Photographic Bulletin reads: "Quite recently many efforts have been made to furnish photographers with a really efficient camera that is truly a detective camera, which while being very compact and portable is at the same time capable of producing work of good quality that will stand enlargement…
"The latest novelty (the Helgelein) however seems to be free from complication...
"For bicyclists and tourists it should prove invaluable. In our hands it has proved very successful."
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