It's a standard Falcon re-cased using a DDD re-casing kit. It's just a pressed steel upper panel that fixes to the front of the original lower case. It included a 6 pin RJ connector for a Mega STe / TT Keyboard. If I remember correctly you had to cut the original upper case in half to fit the thing. The kit was made by a German company called Digital Data Deicke.
If you trawl the archives of Atari mags online you'll find reviews and advertisements for it.
TT030 4mb/16mb/1Gb, Coco. Falcon 030 Stock 14mb (Lynxman), 1Gb CF. Falcon 030 Stock 14mb (Atari) 170mb IDE. Mega 1 (mash up labelled Mega 4) 4mb (Frontier XtraRam w/ SIPPs) ICD ADSpeed ST OverScan. Mega 4 (currently dead), Mega 2, 520 STe (SIPPs), 520 STFM.