What is this?

[Tom K]

It's part of a surveyors theodolite thread accepts a bar to attach to the tripod and the sight clamps on to the OP's wachamacalit. Equerre-Bussole "Theodolite"

 

[Quilly21]

A gift from an elder.

But what is it?

Surveying cross staff

 

[LBCarpentry]

How does it work though??

 

[TheUnicorn]

How does it work though??

my assumption would be, reading the posts here, that you have a post mounted in the ground, the mystery item is mounted on top. looking through the holes, like a basic gunsight, you can give instruction for a second pole to be placed in the ground, say 100 metres away. you can then move yourself around, so you are looking through the other set of holes, giving similar instructions to position another pole. You now have an accurate 90 degree on a large scale. you can then move yourself, lining up to your two new post, and in doing so, create the last corner of a square / rectangle. from that you can plot accurate maps / mark out football pitches / lay out foundations? That would be my guess from the other posts here

 

[Richard_C]

My immediate thought was zoetrope, almost but not quite.