This is a NASA Skylab 4, Crew Signed Prime Recovery Ship (PRS) cover of the Skylab 2 mission, signed by science pilot Doctor Joseph "Joe" Kerwin. The cover is cancelled on June 22, 1973 aboard the USS Ticonderoga which was the prime recover ship in the Pacific recovery force.

Skylab 2 (also SL-2 and SLM-1) was the first crewed mission to Skylab, the first American orbital space station.  The crewed Skylab missions were officially designated Skylab 2, 3, and 4. Miscommunication about the numbering resulted in the mission emblems reading "Skylab I", "Skylab II", and "Skylab 3" respectively.

I obtained this signature personally from Dr. Kerwin via the mail in the early 2000s.  

The cover is in very good condition with a light toning on the back.  Also, it appears that the cancellation was originally faint and someone traced some of the letters of the Ticonderoga in pencil.

I am selling a large portion of my space and aviation collection, so check out my other auctions.