(a) A Reserve officer shall not be promoted to a higher grade unless the officer has been found to be physically qualified and the character of the officer's service subsequent to the convening of the selection board which recommended the officer for promotion has been verified as satisfactory.

(b) Subsection (a) of this section does not exclude from promotion a Reserve officer physically disqualified by a medical board for duty at sea or in the field, if the disqualification results from wounds received in the line of duty, and those wounds do not incapacitate the officer for other duties in the grade to which the officer is to be promoted.