its a magnex, the copys are a difffernt shape, had 4 of these myself, must of been verry popular back in the day as near enough every saxo iv bought has had one fitted,
The magnex only came with a sticker on the passenger side of the tail pipe, wich obviously over time comes off, if you have the time and effort , unbolt the backbox and get yourself some wire whool, a sponge and some vinegar, it will come up epic with some time and love then some polish

irrc none of my magnexes had stamps on the backbox, how ever there was a little plate tack welded onto the center sections of two, the other two had the center sections replaced, wich isnt uncomon as they had tendancys to crack