The nuvistor preamplifiers also used the RCA 6CW4 miniature nuvistor (as used in the converters) which had a very good low noise performance.
I have managed to obtain one of these rather rare units (according to Tom not many were built for the amateur market). This particular unit appears to be for 2m and has its own built in power supply.
The photograph above left shows the 'innards' of the converter with all the components mounted on the lid and the P.S.U mounted in the box. The nuvistor can be clearly seen on the photograph above right (just to the right of the Belling Lee antenna socket). My thanks to Howarth GW3TMP for the converter and the original photographs.
According to an advert from 1964, a 4m version was also available (again with a choice of I.F.s) .
Vern M0WQR has kindly sent in some photographs of a TW nuvistor converter that he acquired at a rally (May 2011) for the princely sum of £2.