I've seen this kicking around the place many times in my life, just ran across it yesterday while attempting to straighten the place up a bit.
I have no idea what it's for, but in checking it out closer I found out it has a few patent mentions, earliest is 1880! The only thing I know about it is that is was my grandpa's (born in 1900)...
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handles at rest
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handles closed
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the screw moves the anvil
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