Key
| Heavy Anti-Aircraft Site |  |
Light Anti-Aircraft Site |  |
Coastal Battery |  |
| Site No. | Name | OS Grid Reference |
| C1 | East Mersea | TM 052 133 |
| C2 | St Osyth | TM 108 126 |
| C3 | Jaywick | TM 149 139 |
| C4 | Little Holland | TM 215 170 |
Coding sequence integral with Chelmsford & Colchester
Gun Strengths
Overlord & Diver
| Dates | 3.7 inch static | 3.7 inch mobile |
| Mar 44 | 0 | 9 |
| Apr 44 | 0 | 9 |
| Jun 44 | 0 | 8 |
| Jul 44 | 8 | 0 |
| Aug 44 | 8 | 0 |
| Jan 45 | 4 | 0 |