I don't have a picture - but I have drawn what I think I remember how it looked like (see attachment).
If you have the standard seat (using this 'pin/bolt') - you will have to remove it and replace it with a different bolt - one that has a recess around it for when you 'hook' the passenger seat into it.
A bit like this one:

(but it's NOT this one - the one you get doesn't have the Union Flag on it!)
Hope this helps?
<edit>
I can photograph it tonight if you still want me too?
</edit>