Eligibility for award, commencing with the period after 31 December 1960, was established by DOD Directive 1348.7, dated 1 April 1966, and terminated effective 15 August 1974, per letter from Manpower and Reserve Affairs, subject: Termination of Eligibility for the National Defense Service Medal, dated 30 June 1974.
According to efile.com, the amount of money a person can make without filing taxes depends on filing status and age. For tax year 2013, a single person under 65 years old had to make in excess of $10,000 before filing taxes, while someone over 65 years old needed income over $11,500 to file taxes. Dependents have a lower tax filing threshold of $6,100 if they're under 65 years old, single and not blind.
Once you reach the year of your full retirement age, yet before the month you reach full retirement, you can earn up to $37,680 without penalty. For each $3 you earn over the limit, Social Security deducts $1 from your benefit amount.