Well, lowendmac groups them thusly:
BTW, AusNick, what model is your "Sapphire"?
/ETA/ Which iMac Is It?
I see four different build dates there for a "400MHz" model. Clearly, speed is not enough to go on.
BTW, AusNick, what model is your "Sapphire"?
/ETA/ Which iMac Is It?