I have one, its got both a peep and a vee notch. They flip back & forth, its really a Hepburn sight. Theres info on it in Brophy's book. It sets too close to the eye to use the notch but the aperature is pretty near perfect.
Theres no windage adjustment but in the days before front sight ramps front sights were commonly used for windage adjustment.
Its on the top gun in this pic,
and the bottom in this one.