To further the confusion that exists with the NASA numbering system as listed above, some cachetmakers went along with the NASA terminology, calling the unmanned Skylab Space Station as Skylab 1, as well as the first manned Skylab flight as Skylab 1, then continued on with Skylab 2 and 3. Other cachetmakers called the unmanned Skylab Space Station as Skylab 1, and the first manned Skylab flight as Skylab 2, with Skylab 3 and and 4 following.
All items are covers unless otherwise noted.
Any cover larger than a number 6 size will be noted or any item of an unordinary size will be so noted. All covers are unaddressed unless otherwise noted. All covers are cacheted unless otherwise noted. A brief description of the cachet is given of the event being commemorated. If covers are autographed they are genuine, unless otherwise noted.