Hans, wellicht heb je hier iets aan?
http://www.nicovandijk.net/converterlenses.htm
Nikkorex-Wide 5.6/38 mm. converter lens en de Nikkorex-Tele 5.6/90 mm converter lens?
For the Nikkorex cameras, fitted with a Nikkor 2.5/50mm., Nikon offered a Nikkorex-Wide 5.6/38 mm. converter lens. This wide-angle converter lens offers a wider (38 mm.) perspective and can be focused down to 36 cm. The Nikkorex-Tele 5.6/90 mm. (see above) can be focused down to 69 mm. Both lenses can be mounted on the camera lens by screwing them on the front thread;
their filter thread is 69 mm. For the Nikkorex cameras, fitted with a Nikkor 2/48 mm. the Nikkor 4/35 mm. and the Nikkor 4/85 mm. were offered. Their features are identical to the Nikkorex converter lenses.
