Gentlemen,
Because I just recently purchase the Canton Reference 3 DC and have the spec sheet in my hand this is what it says: Tweeter: 25mm (1") aluminum-ceramic--oxyd dome, vibration-damped. It appear to be listed wrong on the A4L website which show the 3.2 also with the same tweeter. Anyway, in my opinion, it is a sweet sound tweeter.
What's interesting in the spec sheet is that all of the other speakers listed, the 1 DC, 5 DC, 7 DC, and 9 DC all have the Aluminum-manganese dome.
Regards