Thanks for your comments. However, although I don't know the full history of my 2.5s, it seems highly unlikely that anyone in Argentina would have undertaken such a complex upgrade. Because it involves modifying the crossover as well. I think it was more likely a hybrid pair, released just days before the 2.5i, which already came with a double binding post, came out. It must be said that both tweeters sound identical. But they have traces of dried ferrofluid, as can be seen in the photos. That said, they still sound very good.