I know that there is much confusion on these cars. Have a look here <<< link removed >>>
This apparently has been adopted now in ACD circles as well. These cars change colour, details and appearance quite suddenly if an owner feel like it. The blue car got a different top just recently. (It is all totally unimportant for the identification, which I do not dispute in the least)
First, we don't past links in the puzzles: (see the rules section, please - this is your first warning).
Chrome piping and running lights at the vertical trailing edge of the hood (bonnet):
Present on 2503
Absent on angled bonnet trailing edge 2516 when new, and now.
Trunk covered with the same fabric as the top:
Present on 2503
Absent on 2516 when new, and now.
Twin spares that don't break the plane of the trailing edge of the rear fenders (wings)
Featured (with a bumper) on 2503
Longer trunk, pushing spare tires past plane of the trailing edge of the rear fenders (wings), and no rear bumper on 2516.
I will concede that 2503 has changed color. In each case, the trunk was covered to match the top, and the other features I've listed have remained consistent.