Interestingly, I have both. "Report of birth abroad of a citizen of the United States of America", State Department form FS-240, issued 27 days after my birth, listing all of the particulars.
The document I was referring to is Department of Justice form N-560, Certificate of Citizenship, (stamp)signed by Raymond F. Farrell, commissioner of immigration and naturalization. It was issued on my fourth birthday. One of my brothers was born in Okinowa ten years before me- he got the same certificate, at the same time.
Since you had already been certified as a citizen-at-birth, I wonder what the purpose of the second document was...