Patented Hemispherical EP w crown mark also.what is this ?

[makerseeker]

This is some type of pan with dome cover that opens on both sides and has insert inside with cutouts.On the side it has the triangle mark that says Patented Hemispherical with a W in center of that. On base it's marked T or J then K and N and W all seperate and then sideways from those letters it has EP and a crown over those letters all inside a shield.
I have the rainwater book on silver but could not find this,maybe i did not look hard enough or this is from england ?What would you call this item also and would it be used for muffins to keep them warm?



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