STS-51L - 4" - A-B Emblem "missing star"

The tenth mission for Challenger, STS-51-L was scheduled to deploy the second in a series of Tracking and Data Relay Satellites, carry out the first flight of the Shuttle-Pointed Tool for Astronomy (SPARTAN-203)/Halley's Comet Experiment Deployable in order to observe Halley's Comet, and carry out several lessons from space as part of the Teacher in Space Project and Shuttle Student Involvement Program (SSIP). The flight marked the first American orbital mission to involve in-flight fatalities. It was also the first American human spaceflight mission to launch and fail to reach space; the first such mission in the world had been the Soviet Soyuz 18a mission, in which the two crew members had survived. Gregory Jarvis was originally scheduled to fly on the previous shuttle flight (STS-61-C), but was re-assigned to this flight and replaced by Congressman Bill Nelson

This is a common STS-51L souvenir version from A-B Emblem. The main identifiers are the sewn-on tab and gray line under the yellow path of the orbiter. A newer version from A-B Emblem lacks the gray line. Unlike the crew version, the souvenir version is executed on gray twill. 

I purchased an STS-51L version that was missing a star adjacent to the head of the comet. Easily a production flaw, however, further investigation reveals that at least a batch of these patches were released in this manner (I have found evidence of at least 3), so I found it worthy of note on this site.