A suffix letter may be added to some LIST ID numbers to differentiate between different events, cancels, etc.
All covers are unaddressed unless otherwise noted.
All covers are cacheted and a brief description is given of the event being commemorated. If covers are autographed they are genuine. To conduct scientific investigation of waves and particles in magnetosphere. K ISEE-3 satellite launch, an International Sun Earth Explorer 3 to obtain comparative magnetosphere and solar data, the first satellite to reach point where gravitational pull of Sun equals gravity of Earth and Sun.