Vinegar valentine postcards were usually sent anonymously. They usually featured a large image of a type of person (ie: spinster, occupations etc) with a poem ridiculing or poking fun at that personality. These contrasted sharply with the ornate Victorian valentines sent around the same time.
Today's postcard pokes fun at a male singer by comparing him to a coal salesman!
This great postcard can be found in my eBay store here: VINTAGE VINEGAR VALENTINE COMIC POSTCARD MALE SINGER