Sankey trailer identification help

So I recently acquired a Sankey trailer, I know there are several types and makers of these. Can anyone help Id this one?

It's a little rough, although the chassis and running gear are in good order.

I'd like to buy a cover for it, but a bit of Google and eBay looking suggests different covers for the narrow and wide track variants. How to I know which is which?

It hasn't got it's original lights, it has a tailgate, but no flap for a water bowser, only one leg/stay at the front which might not be original.

It does have a plate on it still, but is very worn. Think I can see "Roots" on it. But not a model or number.

I think that’s a narrow track, roots made wary narrow tracks. The tail gate is weird though as they were usually fixed back