I love this little 1.25" eyepiece... Could never bring myself to get rid of it. Gives super sharp views, But I can't find out any specs (or even a single picture of this model) online.
Carton Erfle 20mm
What would the AFOV be? Field Stop Diameter?
Do all Erfles have the same number of glass elements?
I could guess, estimate or measure those perhaps... But was looking for a manufacturers data sheet.
I'm also looking for another one to try it with binoviewers.