This is a military erfle. According to my measurements, the focal length is 31.5 mm and it has a 69 degree FOV with no field stop. It weighs 11 oz (300g). The view is very similar to a 28mm military erfle that is my favorite wide field eyepiece.
The body of the eyepiece is mounted in a helical focuser ring for diopter adjustment. The ring has 2.12 o.d. threads. To use the eyepiece, you will need to make a 2" adapter for these threads. I would also recommend a field stop at 65 degrees. A rubber eyecup is included. I took it off because I did not find it comfortable.
The eyepiece is coated and appears to be unused. The optics are in mint condition. I am asking $70 including shipping (U.S. only) or best offer in first 24 hours. I am new selling on Astromart, but I can give very good references in another site.