Trade cards were small cards, similar to visiting cards, that businesses would hand out to potential customers and also existing clients. They were popular in London from the beginning of the 17th century. They functioned as advertising and some also carried maps to show the location of the business, (useful as no address numbering system existed at the time).
My own interest in these is that the cards from the late 19th century, start to show businesses from around central London. As the designs became more attractive and colourful, collecting them became a popular hobby, particularly as colour images around this time were not yet widely available. (The selection here are designs I’ve culled from the web, and by no means are restricted to London).
Personally, I’m fascinated by the wonderful trades that used to exist in and around London. I would love to stride into John Moseley’s premises now, and see a shop dedicated to fine woodworking tools, not a scrap of plastic in sight!