Was the 391 line really that terrible? I have not seen many good reviews about them. Was eyeing a pair of old stock Hi hats and have thought twice. Only heard a few vids and sound clips. I see there's a new S line Zildjian came out with this year. Little less tin 12% think it was. But it seems to be sort of the same lathing process and price structure. It's too bad the Project 391 never took off. Sounded like they'd be a bit better when I first read about it a few years ago.
I've only heard a few videos of them but I wasn't attracted to the sound. But my ears are tuned to much darker cymbals.
Project 391 represent Zildjian's experiment with B15±2 once Paiste's patent on that alloy ended. PSA (Paiste Sound Alloy) patent 4809581 granted: March 7, 1989 filed: July 13, 1988 seems to cover B13-B18. Seventeen years is 2006 expiry, but these days one needs to be a lawyer to keep up with which patents run for how many years. It's complicated.
The new S series introduced at NAMM are B12±2 which is a more traditional alloy for Zildjian. Same as the ZHT series.