This information was taken from the Amiga 3000T manual.

Pin   Description
1     Red Video
2     Green Video
3     Blue Video
4     Monitor ID Bit 2 (Ground)
5     Ground
6     Red Return (Ground)
7     Green Return (Ground)
8     Blue Return (Ground)
9     Key (not used)
10    Sync Return (Ground)
11    Monitor ID Bit 0 (Ground)
12    Monitor ID Bit 1 (Not Used)
13    Horizontal Zync
14    Vertical Sync
15    Not Used