MONOTYPE metal arrowhead

[Captain Caveman]

I found this at a house built in 1850. It's shaped like an arrowhead, has the word MONOTYPE engraved in it and has a hole in the top. Does anyone have any ideas on what this could be?

 

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[bonepicker]

looks more like a fishing sinker, or some type of weight.
Never seen one that says mono type.
the word monotype does make me think monofilament.

 

[mirage83]

Plumb bob, carpentry tool for determining true vertical lines. Used with a string or cord and allowed to hang vertically.