tool ID help

[stuckinthemud]

I bought this at a local antiques market thinking it was a plumb-bob but then I found the end unwound, the cylinder was hollowed out and there is a curious slot cut into the thread.  Also, the string, which is currently wound round a piece of 2x1 runs through the end into the hollow.  I wondered maybe its a chalk line, or perhaps the slot is a way of clamping the string off at a desired length?  Only thing against that is there is no spindle to wind the string around in the hollow-space. Can't find any maker's marks, maybe its home-made. Any ideas?

[osage outlaw]

That's a plum bob.  Maybe the slot was for easy string length adjustment.

[Danzn Bar]

Yep that's it.....
DBar

[Hawkdancer]

+1!  Definitely old style.
Hawkdancer

[Del the cat]

I like the acorn shaped top
Certainly better than mine wigh is a bit of old steel bar with a hole though it and point filed on the end 
Del

[stuckinthemud]

Thanks all. It is a great plumb bob, really heavy, and only cost £5 :-)

[ohma2]

Very cool piece,someone cared about what they were producing

[Stoker]

Nice plumb bob. The slot is for ease of unscrewing the top when changing the string. You don't need pliers fingers are good, unless it's rusty
Thanks Leroy