A Complete & Universal English Dictionary (possibly)
First issued as a part work from 1830 to 1836, the "Moule" maps were then used in The English Counties Delineated in 1836 (re-issued 1837 & 38) and in Barclay's Complete & Universal Dictionary (or A Complete & Universal English Dictionary) in 1841 to 1852 (with a [plate] "42" added in 1852), and in Hall's Pocket County Maps (1847) and The History of England by Hall and Smollett in 1849.
Scale correct at 8 miles = 30.5mm, or 6.6 miles/inch, ie 1:410,000.
The florid styled map hasn't changed since before, apart from the addition of some railways - it hasn't got Colchester to Hythe (opened 1847) or Great Chesterford to Newmarket (opened 1848), but does have Witham to Braintree and Maldon (opened 1848) and Marks Tey to Sudbury (opened 1849). Hence, an estimate of 1848.