With regard to the above topic mentioned - just a few extra snippets to enlighten anyone who has naval ancestry or an interest in naval history. My other half confirms that these certificates were indeed issued to prevent people in maritime trade being press ganged into the Navy. The occupations 'protected' included not only sailors, but ropemakers, sailmakers etc - in fact anyone who was connected with the naval industry. These skilled tradesman and seamen were in high demand and many of the best were employed by the major trading companies - who could not only provide better wages but also better conditions for their employees than the Navy could at that time. The certificates were a way to ensure that the best staff didn't get 'pinched' by the Navy gangs. I am also informed that the certificates did a roaring trade on the black market, changing hands for quite large sums, being much in demand with young sons of the gentry as a convenient way to avoid a life at sea! One interesting genealogical point for anyone with a family living in or around a naval area, is the practice of naming several sons after the father.You would find the father John Jones, say, with two or three sons also called John. The reasoning behind this is that said certificate was issued for 'John Jones' (the father) but was conveniently usable for any of the sons too should the need arise!! Incidentally, any other naval or military queries which listers may have are welcomed by said other half Keith, who, as an ex-submariner of 15 years, is always willing to show off his knowledge and help people out! Hope this has interested someone! Linsey, Suffolk