I have a 98 Cobra Drop Top My build number is 1600
I have a plate on my engine with the two sigs on it, but have never heard of a "Signature Series"
It COULD be that, ok, read slowly here: The color Interior, Vert or not, anything else special about the car MAY make it uniquely one of
500 built that same way out of the total build for the 98 Cobra model.
If you find any more info, of course we would all like to hear about it.
Then again, it might be that they guy had no clue what he was talking about and thought that because it has this plaque
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it is something special...?? Of course they ARE special but that's a whole nother story.
Kate