Oswald was discharged in 1959.
There's something amiss.... An enlistee did NOT receive a discharge until he had completed six years of duty. And this form indicates that he was transferred to the Marine Corp reserve where he would have completed the remainder of his six year obligation before receiving a discharge. All enlistees that had not completed the obligated six years when they were released from active duty were transferred to a reserve unit where they fulfilled their tour and then they received a discharge.