(Sorry about the huge picture)
Thanks to Brian Larkin over at
The Tri-State Thunderbird And Cougar Club who provided the best description of what our mystery plate is.
See:
TSTaCC Forums - Ford Plate Decoder Help.
"this picture is of my fathers "93 cobra" h-pipe he bought at a flea market a few years back, the style of the cat tags match the one you have minus the year differnce. Your's is e7, for 87, the ones I have are e8, for 88. Take note the top 5 dgit numebr is the same, most likly that tag came off the pre cat near the manifold."
i9.photobucket.com/albums/a71/BJL88TC/DSCF0001-1.jpg