"This one is not a fake but just badly described. True it is not of Fox Talbot nor a daguerreotype but is a good and genuine example of Claudet's salt print process (used under licence from Fox Talbot)."
Hi Jason, Wonderful to see what a great portrait. As I'm sure you know your John Mansell (1779-1858) was one of 11 children of Thomas Mansell and Martha Price. Thomas Lukis Mansell (1809-1879) was his nephew and an important Guernsey amateur photographer. The daguerreotype is unlikely to have been made by TLM as he did not practice photography professionally and your portrait looks like it may have been produced by one of the commercial photographers operating in the island at the time. I've traced four such photographers in Guernsey in 1848. Contact me via http://societe-jersiaise.org/photographic-archive if you would like more info. Best, Gareth.