The matchlock rifle, often known as an arquebuses, improved on the handgonne by automating the ignition system with a “lock” that held the burning slow match and actuated by a trigger. WEhen activated, the slow match lowered onto a priming pan, igniting a priming charge and eventually the main charge. Most match locks were smoothboare muskets, more often than not these were long arms or carbines, though the Japanese had short, pistol like versions used by mounted cavalry.

Widely believed to have originated in Europe in the mid 15th century and introduced back to China by the Portuguese in the 16th century, the matchlock saw military and civilian use well into the 19th century, despite the introduction of the flintlock in 17th century. Colonial america, Eurpoean armies and eventually Japanese Samurai all used matchlock arms.

Here is a Japanese replica matchlock from the authors collection:
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A close up of the lock mechanism:
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Random video from the the Internet of someone firing a Japanese Matchlock

Links
http://en.wikipedia.org/wiki/Tanegashima_(Japanese_matchlock)
http://en.wikipedia.org/wiki/Matchlock
https://en.wikipedia.org/wiki/Arquebus