Colonel Jack Nesvig was the security chief of the McKinley Rocket Base during the 1960s.

In 1968, he inspected an orbital platform together with Cromwell shortly before launch and later questioned the captured Captain Kirk and Spock. (TOS: "Assignment: Earth")

Colonel Nesvig was played by Morgan Jones.
Although noted in the credits as a colonel, close examination of the scene suggests that the character is a security guard given the hat with the numbered badge and what appears to be a security guard patch on his white shirt.
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