RAMC sleeve badges

[High Wood]

Could anyone please define the period that these RAMC sleeve badges were worn?

I know from photographic evidence that they were worn during the Great War and possibly just before but for how long afterwards? I cannot recall seeing WW2 photographs of them being worn.

Secondly, is there any special significance in the colour of the backing cloth, black on two and Khaki on one?

Are they likely to be Great War period?

Thank you,

Simon