i doubt that it is the original system. it should be stainless. second it would have three 02 sensors. third. the two cats would have been stamped and numbered. fourth the original would have the woven mesh flexi. the clamshell back box has already been changed by the sound of it. but i would suspect that it has had a cheaper all in one system fitted without the third post cat o2 sensor. that would have been inline approx with the rear lower engine mount. it may be plugged off with a bolt or was never there. if the wiring for this has been doctored or looped in , you would need to see underneath. all sounds a bit strange to me ...
