(6 cards individually bagged with envelopes and header) OUTSIDE GREETING: With Best Wishes!~~BLANK INSIDE~~This image hails from the golden age of the picture postcard, the early 20th century, when as many as a billion postcards were mailed per year. Postcard printers competed to produce cards for every holiday, and St. Patrick"s Day was no exception. This particular postcard features children bearing four-leaf clovers.