In reply to Annie (Reply 16). Like you I have looked up dozens of Scottish 1855 Birth, Marriage and Death Certificates. My own 2 x Great Grandmother died 1855 and her D.C. lists her children in order, their ages and whether alive or deceased. 1855 Marriage Certificates carry a lot of information, including birth place of bride and groom, and says if birth not registered.
Out of curiosity I have now looked at the 1855 Marriage Certificate of Peter Morrison and Anne Larnock. Under the column headed, 'Birthplace, and when and where registered.' for Peter Morrison it says, "Born but not Registered on January 15th 1820 at Sutherlandshire, Scotland." For Anne Larnock, "Born on May 1st 1822 at Lerwick, Shetland."
Regards, Dod.