Unidentified Royal livery button
 

I have not been able to identify this button.
It is 24 mm and has a complex design, divided with 2 labels (5 points and 3 points)
Made by Firmin & Sons, 153 Strand

Anyone?

Some observations as I'm not by any means well up on heraldry.

The coronet above the shield and also worn by the lion supporter on the left is that of a Prince or Princess of the Royal Blood, being the children of the Sovereign, except the Heir to the throne who has his own crown.

The shield itself is lozenge shaped which as I understand it signifies a female with their own arms.

Firmin & Sons became a limited company in 1875 so is it before that year?

David.

Thank you David,
I missed that the lozenge is a coat of arms used by females.
I agree it is pre 1875 because of the Firmin & Sons name.

I am plodding on, not being an expert.
This is how far I got:
It is a divided coat of arms.
Does it show the coats of arms of her parents, both members of the royal family?
The dexter side (left for the viewers) has a label of 5 points: a grandchild of a sovereign.
_________
| | | | |
The sinister side has a label of 3 points: a child of a sovereign.

Presumably from the time scale we are looking at one of Queen Victoria's children? I suppose the next step would be to check the arms of each of them.

David.