Wiedmann
From CPCWiki - THE Amstrad CPC encyclopedia!
A german company that produced the Wiedmann BTX Modul for Schneider Joyce. Wiedmann is listed as provider for some Amstrad support/spares on Cliff Lawson's semi-official Amstrad page, http://web.ukonline.co.uk/cliff.lawson/.
Wiedmann still sells Amstrad/Schneider hardware and software. They do not have a catalogue, but they have lots of products available on request (as of 2009).
The company does still exist in 2010, and they do even still have Schneider and Amstrad logos on their webpage: http://www.wiedmann.com - however, they seem to be focusing on older (pre-computer) hardware now, see screenshots below.