Can anyone help identify this piece of glass?

[RomanYalowitz]

Hey Yall....

my aunt just recently gave me a beautiful Graflex speed graphic that is in amazing condition, I am psyched to start shooting with it ASAP...

Anyways inside the box I just today found a third lens hiding....

Its kind of a mystery and I just dont really know what it is and I cant quite find anything about it online, and there are pretty much no engravings on it.
It looks like it could be a really amazing wide angle lens but it seems like its missing some stuff and I just need some help with it.
Below I will attach some photos and if anyone recognizes anything, that would be a tremendous help.

What is engraved on the front is;
" 6in. f/2.8 NO.1722 FD 4.495 in. part no. 412206-1" nothing more at all, and on the back there is a V above 17 inside a circle....
photos below..
It also has kind of an interesting shaped back, its more of a cone shape, and I cant seem to find much else that looks like this.
Thanks

[Dan Fromm]

It is probably the front half of an aerial camera lens. I say probably because these beasties usually, not always, have three pins spaced 120 degrees apart around the front. Whatever it is, it is half of a lens. Best use, paperweight.

[Dugan]

I concur with Dan.
Most likely the front half of a military surplus aerial camera lens...probably used for photogrammetry.
Looks like it's pretty scratched up.
If you're looking for a research project, you could Google "Metrogon lens"...this is not a Metrogon, but it's probably a distant cousin used for a similar purpose.

[RomanYalowitz]

Sweet.
Thank you guys for the responses.
I am going to try and look a bit deeper and what you suggested @Dugan....

One last question would be; how many components potentially is this missing?
I have a friend that started machining small precise components, is it worth maybe trying to get him to cook me up a couple pieces to try and be able to mount this thing, and use it kind of just wide open like it is....?
Thank again for the help.

[RomanYalowitz]

Continued.....

I was thinking if I could find a way to mount this to a lens board for the 4x5 Graflex I could just use it wide open and be able to fire the shutter from the backend of the camera, using the curtains, and the one(camera) I have is wicked fast still....
Just my thought process here.

So if anyone would potentially know what it may need to be able to be mounted to a lens board?
I just kind of half tested it, held it in place in a lens board and looked through the back of the camera, and it seems like its pretty close to working.
I think I will try and figure out how to mount to a board and take any suggestions if they come!
Sweet
Thanks

[j.e.simmons]

It would be worth experimenting. You can cut a lens board easily for that camera from a piece of model airplane plywood.