I should have added, the second mark is the crest of the City of London, and the third, the arms of the City of London.
Here's some more examples:
Barnard's plating side of their business was thought to be operating sometime during the 1850's/1860's period. The plating works were set up by Michael Farraday. The Barnards and the Farradays were connected by marriage on several occasions, John Barnard (I) married his sister-in-law, Margaret Farraday, the sister of Michael Farraday on the 14th March 1826. Michael Farraday was married to Sarah Barnard on the 12th June 1821.