A man born in 1887 would generally need 6 quarters of coverage to be fully insured for Social Security under the old rules that applied to people born in 1893 or earlier. The SSA rule table lists Jan. 1, 1893 or earlier = 6 quarters for workers reaching retirement age.

Why that number is low

For people born before 1930, Social Security did not use the modern “40 credits” standard. Instead, the required quarters depended on birth date and the older insured-status rules, and the minimum shown for that era is 6 quarters.

Important caveat

That answer is about being fully insured under Social Security’s historical rules, not about modern retirement eligibility. Today’s usual retirement standard is 40 credits, but that does not apply the same way to someone born in 1887.

Plain-English version

So the short answer is: 6 quarters, which is about 1.5 years of work if each quarter was credited.