Greetings.
Andy, as Luke has stated, this badge was/is one from a large collection of badges, the vast majority of which were/are bogus/fake/counterfeit/fantasy items that were sold to this seller.
Many of them were offered on ebay and with the exception of a very, very small number, they were not genuine/original items.
The badge you have stumbled upon is a poor cast copy of an Officer's OSD badge, made by Ludlow, with London following the name which is missing from the cast, but London remains.
Below is an example of a genuine Officers badge, of the same pattern, showing the maker's mark but produced in white metal and on blades.
IMG_5169.jpg
IMG_5170.jpg
I hope this helps you in choosing a genuine badge in the future.
Also, if you have an interest in Essex Regiment badges, have a look at my album
here
Regards.
Brian