Vintage National Accelerator Laboratory A.E.C. Optical Device maybe Spectrometer For Sale

This is some type of optical unit that is from the National Accelerator Laboratory A.E.C. I do not know what this is or what it it may have been part of or used for. This does not have a manufacture or model number marked on it. It just has the National Accelerator Laboratory A.E.C. asset tag attached. The only numbers marked on this is on the small end, it ia marked 173 on top and 240 909 on the bottom. This is a very interesting item. when looking into the large end you see a green image on the outer edge. In the center is a small square. This is a heavy unit and comes with a heavy base. The base has four ball bearings so the unit can be rotated easy. The large black lens on this can also be rotated easy. This may be just part of a larger device or maybe there is something missing on the smaller end. The smaller end has threads for something, these are a little damaged. When looking through this the optics are clear. I hope that someone knows what this is and what it was used for. This unit is 24 inches long. The large end is 2 3/4 inch diameter. The small end is 3/4 inch diameter. This unit weighs 11 pounds. The base weighs 15 pounds.