A Note on Skylab Mission Numbering
The official numbering of Skylab missions has the launch
of the orbital workshop as Skylab 1;
and the three subsequent crew launches are designated Skylab
2, 3, and 4. A parallel, "unofficial" numbering scheme denotes
the three crew launches as Skylabs 1, 2 and 3, leaving the
OWS launch undesignated. The crew patches follow the unofficial
numbering scheme. This site uses a compromise scheme: like
the International Space Station flights, "Expedition"
numbers are used. Thus Skylab 2 is referred to as "Skylab
Expedition 1", and so on.
In Homesteading Space, a history of the Skylab Program, the reason for the discrepancy is explained (pp.61-63). The crews initially designed patches around the official 2-3-4 numbering scheme, but when they asked the Skylab Project manager to confirm this numbering, they were told to use 1-2-3. They then re-designed the patches using the 1-2-3 scheme, had the artwork prepared, and sent it all to headquarters for approval. The designs were rejected, on the basis that they should use the official 2-3-4 scheme. The crews had begun the process of having artwork prepared for the 2-3-4 scheme, when they were told "not to bother."
The reason was simply practical: the complete crew provisions of food and clothing for the entire length of the 3 missions were to be stowed aboard the OWS prior to launch. Naturally, this required considerable lead time, and the process had gone ahead without waiting for official approval of the patch designs. So by the time headquarters vetoed the 1-2-3 designs, the clothing (complete with insignia) had already been produced and shipped to the Cape. NASA managers decided that the expense of having it all changed was prohibitive, and so they dropped the matter.