From memory, a double-focusing (magnetic & electrostatic sector) mass spectrometer should routinely give 5,000-10,000 resolution; fine-tuning could give up to possibly 25,000.
Accurate mass measurements are possible at much higher mass than 2-octanone/naphthalene, but above about m/z 500 there are so many possible elemental compositions (which is why you measure an accurate mass) that acc. mass is not as helpful as you might think.