I'm not sure where to post this so feel free to move it.
The dish has no marks at all. The paint has worn away. I think that's honey gilding around the edges, etc (correct me if i'm wrong). It has holes in the back for hanging to a wall. I have seen similar coin plates made by Royal Copenhagen so I wonder?
The coin reads: "FREDERIK VIII KONGE AF DANMARK". I've seen similar ones with the head facing left but can't seem to find this version of the mould. I'm not sure if it's even a coin. It's either a very thin one or it's sunk into the porcelain. I ran it through my metal detector and it says it's either gold or bronze. There are no date marks or mint marks, at least on that side anyway. I guess it dates between 1906 to 1912 (FREDERIK VIII)
Cheers, Tony.