Frog Surprise Mugs - Yellowware, mid-late 19th century - Possibly Baltimore Pottery

So...if anyone has an in depth knowledge of the production of these frog mugs in America please comment below. The two mugs are remarkably similar, yet different in some key ways. The brown mug, I believe, is American, perhaps Baltimore Pottery. These frog mugs were made there in the 1850's, they are not that common, but I don't know if they are quite "rare". There were, also, some yellow ones made, although not in Baltimore, in America (the name of that pottery I will intentionally leave out). Yellow mugs made in America are nearly impossible to find. I haven't even seen a picture of one.

I do believe this yellow mug to be English. It is made of a white ware that looks like porcelain, while the brown mug, I believe, will be of a softer yellow clay. It is just that they are so similar in design, layout, technique, etc. that I should not yet rule out American ?????? I am confused. Please feel free to comment.

Thank you.