Can anyone suggest what the lid is?

I have a small round box, could be for snuff or pills, the base is very clearly marked as C.H next the british lion the the three wheat sheaths of Chester and the letter W.
So I think it’s Charles Horner, Chester 1922. but the top of the box is the problem it is a translucent pale green, I suppose it could be Jade but 1922 could it but early plastic? but then the question is would CH use plastic! Hope someone can help.

I think your lid is green Agate, which is a native Scottish stone.

Thank you bluerinse, I don’t think it’s stone. I say this because it feels warm rather than what I would expect from stone (cold). Having thought about the age of this piece I am more convinced that it could be (Plastic). I put this word in brackets because in the 1920’s
it was just after the ‘Bakelite’ invention and the start of the plastics revolution and Charles Horner was fascinated with this new substance.