This is an Erfle 31mm focal length, used, 2" barrel diameter eyepiece for sale. And I note that it has nearly full barrel diameter optics.
And it has though a bit of lens haise...and the barrel near the front-end is sorta got some places where someone tried to attach it to
something with rubber cement. However those areas seem solid and not much ever comes off.
It's got some etched info on it, yet some of those regions are covered by that afore-mentioned area of rubberization.
Filed under: Eyepieces & Accessories