The first official record we can find on John Barlow was a record in the 1841 United Kingdom Census where he was 60 years old and still working as a jeweler (and lodger) at James Street, St Marylebone United Kingdom.  From previous works we know his work started around 1800 and continued through 1841.  His early works tended to use seed pearls to craft his pieces which took extreme amounts of time to drill and manufacture the gold to fit.  Barlow passed away in 1853 at 73 years old.