Phone Gong Ringers

I've been wondering, does anyone happen to know if the gong ringers inside old phones (those loud and annoying bell ringers) have been standardized over the years? And if so, what note are they tuned to? Right now, all of the one's I have lying around sound about the same. I've been thinking about searching for my old guitar tuner and trying to figure out a more exact tuning with that, but I'd figure I would ask first. This seems like the pointless sort of knowledge someone here must posess.

VIRON9 years ago
I don't know the notes although there are 3 I'm aware of and they are marked A B C. If that is the note, that would be nice.