Le compte D'Essex
Latitude & Longitude marked, but London is at 32o 45' east, so prime would be off the Azores(?).
First map that metions the North Sea (or at least "Mer du Nord").
Displayed scale of 9mls = 31 mm, or 7.4 miles/inch; scale actual = 9.1 miles/inch, or 1:575,000.