I believe the embossed seal concern can be answered according to the date of issue, 1966 v. 2011.
Currently acceptable forms of certification include a stamped, multi-colored seal (signature stamp).
That said, the “new” COLB released by the WH shows a grayscale (B&W) seal. That may be explained due to it being a photocopy onto safety paper. Which means that the seal was on the security paper -underneath- prior to the photocopy of the “log-book” COLB.