Kodak -2 Telek adapter lens
We often use positive lenses as accessory lenses, usually as close-up adapters. Kodak Telek lenses (sadly no longer made) were negative adapter lenses. This one fits "series VI" fittings and is -2 dioptre.
I fitted mine to the back (film side) of my Tench lens. It was quite a good fit, and as the Telek is rather light, some blu-tack was all I needed to secure it perfectly well.
13th October 2012. Olympus E420 with 14-42mm kit lens.