wheel lock

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A firing mechanism in certain obsolete small arms, in which a small wheel produces sparks by revolving against a flint.
• noun A firearm using such a mechanism.

from The Century Dictionary.

• noun A lock for firing a gun by means of the friction of a small steel wheel against a piece of sulphuret of iron (pyrites).
• noun A combination-lock or letter-lock.
• noun A form of brake; a wagon-lock.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an obsolete gunlock using flint and a revolving wheel