A permit is valid for each handgun legally in the possession of the person to whom the permit is issued. Subject to subsection (c) of this section, a permit issued under this subtitle shall restrict the wearing, carrying, and transporting of a handgun by the person to whom the permit is issued to wearing, carrying, or transporting a handgun concealed from view: under or within an article of the person’s clothing; or within an enclosed case. The requirement in paragraph (1) of this subsection to keep a handgun concealed is not violated by: the momentary and inadvertent exposure of a handgun; or the momentary and inadvertent exposure of the imprint or outline of a handgun. A person is not subject to the requirement in subsection (b) of this section to keep a handgun concealed if the person is authorized at the time and under the circumstances to wear, carry, or transport the handgun as part of the person’s official equipment, and is: a person exempted under § 4–203(b)(1) of the Criminal Law Article; a security guard licensed under Title 19 of the Business Occupations Article acting within the scope of employment; a correctional officer or warden of a correctional facility in the State acting within the scope of employment; a railroad police officer appointed under Title 3, Subtitle 4 of this article acting within the scope of employment; or an employee of an armored car company acting within the scope of employment.