What you have is very likely a GE panel.
The breakers are actually four single pole 100 amp breakers rigged with an internal common trip mechanism and set up in such a way that two 100s are paralleled on each phase giving a total ampacity of 200 amps per phase.
I have this very panel in my own house.
[This message has been edited by iwire (edited 04-10-2006).]
