The registrar, the doctor and the parent are all put on there at birth. The ONLY thing that would be different from year to year is the signature of the one who signed and stamped the certificate certifying that it is a certified copy requested in that particular year. A registrar in 2001 can not certify ANYTHING about a birth even 10 years ago - only on the date of the child.
In 1966, the Director of Health and the Registrar General can certify that the copy of a 1961 COLB they are sending out is an authentic copy. Just as the State Registrar in 2011 can certify that the copy of a 1961 COLB he is sending out is an authentic copy.
The two signatures at the bottom of the Nordyke image only certify that the COLB above was an authentic copy of the original form. The Onaka signature at the bottom of the Obama image only certifies that the COLB above it is an authentic copy of the original form.