Okay Brother, since you asked. Please dont treat it as a definite guide to buy a 718 pair. The most important factor is how the pair sounds after install.
For starters, the original 718 frequently referred on the forums is the one with black logo as shown below.
However, these were later replaced by a blue/silver logo on the back. To recognize an original 718, you have to look closely at the glue application around the rubber surround. It should be uniform. A no.1 copy will have imperfections on either end.
Then observe thickness and quality of the logo on back. It should have a metallic touch to it rather than just a card sticker.
Then observe the crossover, the inductor should be wound and soldered pretty neat. Also, the glue beneath the capacitors should have an even spread.
Whatever the case, the final verdict comes by putting this pair in an enclosure with a Kenwood/JVC/Sony amp. Play "Bally Sagu's: Chura Liya Hai". The bass should be robust and penetrating through your chest without the use of a woofer. Even at max volume(right before distortion), the low note should play happily everytime.
Finally coming to your actual question whether you should buy it or not. You see brother, rubber hardens over time. Below is the pic of a pair bought in 2009. The rubber surround eventually gets dull, hardens and then develops cracks after couple of years. Since the one offered to you is 2004-2005 manufactured, spending 5k on it is not advisable. Buy a new pair, like Pioneer 6975 or 6902r and enjoy your investment.
P.S. If anyone from the SQ club see me here, I am grounded for good :-)
