I've just got one vintage eyepieces of this type/size as follows:

- Application - microscope or telescope
- Magnification = unknown but high magnification - focal length shown as = 12.5mm
- Diameter = 24.09mm
- Depth of fit = 25.75mm

No maker's name that I can see, but a quality vintage piece.  Needs a light internal clean.

The eyepiece will be well wrapped and shipped by Royal Mail.

Thanks for looking.