These are Enamal signs that used to adourn nearly all English shop fronts in late Victorian/Edwardian times these are now known as street jewelry & are avidly collected in England although this is a small example larger pictorial ones fetch large sums of money
Magic Baking Powder was first made in Canada in 1897 by the E. W. Gillett Company in Toronto, and later bought out by Standard Brands. The brand is now owned by Kraft; a factory in Exeter, Ontario produces it for the Canadian market, as well as making Davis and Fleischmann brands of Baking Powder for the American market. Though the tin is now plastic, the label has not changed (apart from being Frenchified and metricized.) In the 1980s, a representative from the Magic Baking Powder company appeared as a guest speaker at a lecture for MBA students at the University of Western Ontario. The speaker asked the students in the lecture hall how many of their mothers used Magic Baking Powder. No one knew. He held up a tin of it. Every hand in the hall shot up. "And that", he said, "is why we'll never change our label." FROM HERE
I hope that helps.
Cool sign! That size sign is known as a door push, they would be attached to the front door of the store where everyone pushed on it (makes sense). They sometimes came in pairs, one for each side of the door. I once dug two little Fleishmans Yeast signs that way - they had thrown the whole door out!