This ad appeared in the July 1819 issue of La Belle Assemblee.
I found two 1844 ads for Dunn’s spices in different books:
Pentonville Road was an 18th century bypass of Central London, named after the new town Pentonville, that aimed to move manufacturing from the city into suburbia. Daniel Dunn had a cocoa factory at No. 9 Pentonville Road beginning in 1833, that would last until about 100 years later.
More information and a picture painted from the viewpoint of the cocoa factory roof is available here: Pentonville Road | British History Online (british-history.ac.uk)
