What is this optic?

[ManFromMars]

Hello, I've come here hoping that someone could help me identify what this optic is. There are no markings. Tube is .75" . It's 17.25". There's a lens at each end with a hole in the center.

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[dhagerty40x]

That is what is known as a King tube.. It is basically an iron sight.

[Jimologist]

Its not really an optic. There isnt any correction or magnification. It adjusts with the elevation and windage knobs like a scope but it used inserts like a peep. The one i had even had post inserts like a Lyman or Anschutz globe front sight.
Dan is correct, it was actually considered an iron sight for classification purposes. Still unlimited but not a scope because no magnification or glass

[ManFromMars]

Thank you, very helpful.

[aggshooter]

They made interchangeable inserts of various peep hole diameters, as well as inserts configured for conventional front post and rear notch, some were oversized so you could use a file to create your desired post and notch widths.