This is basically a soot card joke. The instructions on the envelope say: “Hold in a good light and see if you can read correctly the words on this card”. As the reader twists the card around to read the message they get their fingers covered in soot from the back of the card. The Windsor Novelties operated around the start of the 20th century. This particular item is shown in their catalogue of 1914. The business was subsequently bought by Davenports.

This set was manufactured by The Windsor Novelties, a company in Eton, Windsor, England. An advertisement in their 1914 catalogue, illustrated, explains that the box comes in two sizes. Their business was subsequently purchased by Davenports.