The 109 was the 300se, 300sel, 300sel 3.5, 300sel 4.5 and 300sel 6.3. The basic difference between a 108 and 109 is the air suspension. 108 has conventional coils, 109 air suspension.
The 6.9 is a 116 not a 109.
As far as the hand built issue, I believe the 116 was the last of the hand built cars. When the 126 dubuted in europe in early 1980 a new facility in Siengefelden was used and it had a great deal of automation. If I am wrong someone correct me please.