The Atlas was first published in 1837 (Essex is dated 1835), and then several times to 1871 (or later), as Hobson's Fox Hunting Atlas (1850 to 1880), as Walker's Fox Hunting Atlas (up to 1895) and as Lett's Popular Atlas (1884 & 87). This example is an 1846 map dissected on cloth and sold folded up between boards, with later annotations.
Hundreds referenced to a table, plus listing parliamentary boroughs, places of election and polling places. Hundreds uncoloured, but Colchester, Harwich & Maldon Boroughs all blue-lined. Six Polling Places in North, 7 in the South. Divisions edge coloured, with a faint dashed line for the boundary. Major roads have a thicker line on one side and coloured pale brown.
Displayed scale of 1+12 miles = 83mm, or 4.0 miles/inch; actual scale = 3.9 miles/inch, or 1:250,000.
Railways have quad lines with red overlay for West Ham to Plaistow (authorised 1844; opened 1846), north Colchester to Hythe (1846; 1847), and the Grosvenor House-Red House & Ilford-Red House, plus Red House to Epping (missing Loughton) - all authorised 1846, but never built. There are red lines with no underlying black lines (& generally drawn rather approximately) for Braintree to Witham to Maldon (1846; 1848), Marks Tey to Sudbury (1846; 1849) and from Chapel to Halstead (1856; 1860), . The faint pecked black line from Romford to Thames Haven Docks has no red overlay.
Compass rose still in Herts.
"By J & C Walker" under the cartouche, but along bottom "Published by Longman, Orme, Rees & Co, Paternoster Row, London, 1846." Manually dated April 23 1847 on back. From this and the the red lines, I estimate its selling date as being c.1847.
Many J&C Walker maps are shown on the Walker's Map Publisher page.