If you remove the black cloth covered box on the back of your Plat's you will be able to see the backs of all the woofers. If all the markings are the same, then you're good.
Anyway, looking at your markings I would say, yes that one is original. However, I think you may have left out a "0". The top number should be 618-00003-00.
A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
richP is a lying POS