The Amstrad CPC 6128 is the successor of the Amstrad CPC 664 which had a 
very short life.
It has almost all the same features than this last one, except the memory.
Only 42 KB (idem the 664) can be accessed, the upper 64 KB are used as
ramdisk or to store datas.
It was sold with a mediocre monitor (monochrome green or color) and a
built-in 3' floppy disk drive (160 KB). 

It runs under Amsdos (the Amstrad Operating System) or under CP/M 2.2 or
CP/M 3.0 (CP/M +).
The CP/M 2.2 was bundled with DR Logo and CP/M + with GSX
(the graphic extension of CP/M).
As the CPC 664, the Amstrad CPC 6128 is almost fully compatible with the
CPC 464. 

The German version of the Amstrad (Schneider CPC 6128) has different
"real" connectors instead of mainboard edge connectors.
Norbert Unterberg report us that the main reason for this is that the
original Amstrad did not pass the german "FCC" test because it was
polluting its surrounding with electromagnetig waves, and the rules
for that were much stricter in Germany.
That's why the Schneider got real connectors and a metal housing inside.
However, After "Schneider Rundfunkwerke" stopped selling the Amstrad
CPC series of home computers and the PCW series of word-processors,
Amstrad continued to sell the CPC under the Amstrad brand name in Germany. 

The ROM is identically for all brands of Amstrad: Schneider, Amstrad.
There are three jumpers on the main board which decide what company name
it displays on power-on. 

(www.old-computers.com)