Lufkin tool

[blackoak]

Got this in a box of goodies from a local auction. It is marked Lufkin so I assume it has something to do with use with a tape measure, but how and why. Only one of the arms is moveable

[lptools]

Hello, Blackoak. That is most likely a Lufkin N0. 584 Clamp Handle. Regards, Lou

[blackoak]

That is it. I guess it is for gripping the steel tape for pulling it out for your measurement

[oldgoaly]

maybe a helping hand for those long 50-100 foot tapes?

[gibsontool]

I have a couple of those around here some place. Now I finally know what they are for.

[Yadda]

Neat gizmo!

[J.A.F.E.]

They are still available but you might want to sit down before pricing one.

https://www.industrialhardware.com/584-037103453143-up.html

[Northwoods]

Holy cow! 
It would only make sense to have one if you were working production and used it all day long.

[Bill Houghton]

For a good deal less, you could get any number of soft-jaw quick-release clamps that would do the work.

[Redneck Albertan]

In a past life I was a surveyor. We used those clamps to hold on to the chain (steel tape). The chainman at the front used the tension handle to put the proper tension on the chain so the measurement was accurate. Now everything is done electronically.