The British Magazine and Monthly Register of Religious and Ecclesiastical Information
Not a map of Essex, but instead a map of the Diocese of London (which covers most of Essex), showing Archdeaconeries and Rectories/Vicarages/Cuarcies/Chapels of Ease.
Scale correct at 12 miles = 32.5mm, or 9.4 miles/inch, ie 1: 595,000.
The Magazine published maps of each Diocese over time.