Rob,
Some of these fakes have been around up to 50 years and turn up broken and damaged now so condition in that respect isn’t a barometer for originality.
The badge is from the same die as Martin Marsh one even down to the seeding pattern. That your badge has the same flat, shallow strike as seen on all the others on eBay, it’s undoubtedly not original and one of Marsh’s wares I’m afraid.
https://www.ebay.co.uk/itm/THE-ESSEX...cAAOSwo0JfxqOr
https://www.ebay.co.uk/itm/WW1-Essex...Cclp%3A2334524
https://www.ebay.co.uk/itm/BRITISH-A...YAAOSwWelfb1Sy
Keith is extremely knowledgable and a real gent but not infallible. I’ve seen large parts of his collection during our correspondence and picked out a couple duds. In this instance I’m certain his initial incline was correct.
I would be very interested to see the picture and will drop him a line.
Previously I have seen ‘docked’ examples of the flat top crown 1916 versions with the DET scroll removed. The outline shape would appear very similar, albeit it’s voided. That may even be what Marsh based this fake on.
Luke