noise filter???

on a stock distributer (1957 and others)..... what is the condenser mounted on the coil bracket for? i thought is was a "noise filter" or whatever you want to call it< but im not sure. i just picked up a few parts from the boneyard including then a "874" distributer and coil mount. also does any body know the differances between the standard coil vs. hi-po coil? and there related parts? i was looking for the actual measurements of resistance and/or ratings between standerd vs. hi-po. thanks