This is a trade card, not a postcard. Trade cards were popular from about 1870 to 1890 as advertising and as collectibles. In most cases it's clear what was being advertised, but there may also have been businesses that gave cards out to customers without their business name. It's also possible that this is a sample card, before imprinting. Or, perhaps the artist was advertising, although I couldn't find out anything about E.E. Manly.
It may seem odd that the young lady is holding a squash racket, but squash was starting to gain in popularity in the 1880s.
Here's the back of the card.