I was in the Navy 1959-1963. How do I know if I qualify for extra S.S. benefits.
Hi. If you were on active duty during those years then Social Security would add deemed military wages (DMW) to your actual earnings in those years (https://www.ssa.gov/OP_Home/handbook/handbook.09/handbook-0953.html). Those extra deemed wages could then be used when calculating your benefit amount, but whether or not that would actually increase you benefit rate depends on your full earnings history.
If you're already collecting Social Security retirement benefits, Social Security should be able to access your records and tell you whether or not DMWs were already credited when calculating your benefit rate. If not, you could ask them to recalculate your benefit rate with DMWs included. In that case they would need to see proof of your dates of active service, such as a copy of your military form DD-214,