If this post is still "open", I offer my experience:-
My parents received a "Cetificate and Record of Birth" from the Middlesex County, NJ Health Dept., at New Brunswick, based on the "Certificate of Birth" form initiated by the attending midwife and completed by my fther. Dr. G. I Cronk, Middlesex County Health Officer and Registrar, issued the State's document. There were two clerical errors that I decided to correct in April 1947. I went to the NB,NJ County office. The clerk opened the bound register to my birth-date page that was filled with Dr. Cronk's unique handwriting. My birth was not recorded. As I stood there in front of her with a Certificate, she had no choice but to leaf through the huge volume until she came to June 1946 entries, long after Dr. Cronk's tenure, and there found the birth record entry by a contemporary clerk. A colleague then commented that that was the period when all birth registrations to a certain designated date were shipped down to the State Archives at Trenton. I went to the Archives. The clerk there found the original form; corrections were made via appropriate form handed me.