AMX Mouse:
    CB1     X axis
    CB2     Y axis
    PB0     X direction
    PB1     -
    PB2     Y direction
    PB3     -
    PB4     -
    PB5     Left button
    PB6     Middle button
    PB7     Right button
    5v      Power
    0v      Power

Marconi RB2, Master Compact:
    CB1     X axis
    CB2     Y axis
    PB0     Left button
    PB1     Middle button
    PB2     Right button
    PB3     X direction
    PB4     Y direction
    PB5     -
    PB6     -
    PB7     -
    5v      Power
    0v      Power


This table is an addendum in my New Advanced User Guide:

9D  BBC       Atari    Amiga
-------------------------------------
1   Xdir      Xdir     Ydir (Vert)
2   Right     Xaxis    Xdir (Horiz)
3   Middle    Ydir     Yaxis (VertQ)
4   Ydir      Yaxis    Xaxis (HorizQ)
5   Xaxis     Middle   Middle
6   Left      Left     Left
7   +5v       +5v      +5v
8   0v        0v       0v
9   Yaxis     Right    Right

Atari->BBC   Amiga->BBC      BBC->Atari    BBC->Amiga
----------   ----------      ----------    ----------
  1 -> 1       1 -> 4          1 -> 1        1 -> 2
  2 -> 5       2 -> 1          2 -> 9        2 -> 9
  3 -> 4       3 -> 9          3 -> 5        3 -> 5
  4 -> 9       4 -> 5          4 -> 3        4 -> 1
  5 -> 3       5 -> 3          5 -> 2        5 -> 4
  6 -> 6       6 -> 6          6 -> 6        6 -> 6
  7 -> 7       7 -> 7          7 -> 7        7 -> 7
  8 -> 8       8 -> 8          8 -> 8        8 -> 8
  9 -> 2       9 -> 2          9 -> 4        9 -> 3

At least they all have +5v and 0v in the same place, but that's
because they were all commandeering a joystick port.