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

- Application - microscope/telescope
- Magnification = 78x - very high power - 10mm focal length
- Diameter = 22.93mm
- Depth of fit = 22.5mm

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.