This postcard advertising Hallmark Christmas cards and the "delightful Hallmark Jack-in-Box Christmas Card Holder (150XCH17-3)" was mailed by a store in 1964. There is an advertising message printed on the back with space below it for the store name.
The Hallmark Newsroom website has an interesting page about Christmas Cards Through the Years, a descriptive listing of styles and subjects of Christmas cards from each decade since the 1920s. Over the years, Christmas cards have reflected the traditions and trends of society.
Another page of the Hallmark Newsroom lists some facts about Christmas cards.