My word. I was growing up in the 1950's and actually remember this. Not sure when it started or ended.
The cost of a post card in 1965 4 cents. It want up to 5 cents in 1968. Prior to that the 3 cent rate was in effect for 5 years.
Watercolor Postcards - 2013 was released on: USA: 4 October 2013 (San Diego Film Festival)
The ISBN of Postcards - novel - is 0-00-654668-4.
Postcards from Buster - 2004 Family Reunion Nashville Tennessee 1-35 was released on: USA: 4 February 2005
Postcards from Buster - 2004 The Case of the Coin Purloined Fort Leonard Wood Missouri 2-4 was released on: USA: 18 December 2006
10 Cent Pistol - 2014 was released on: USA: 4 July 2014
AOL Sessions - 2002 50 Cent was released on: USA: 4 February 2005
The Gallant Men - 1962 The Ninety-Eight Cent Man 1-4 was released on: USA: 26 October 1962
50 Cent The Money and the Power - 2008 Respect the Hustle 1-4 was released on: USA: 5 December 2008
Postcards come in many sizes, depending on the country and the design. However, most postcards are 5"x7". However, postcards can be as small as 4"x6", or as large ad 6"x11", and still be considered "standard". Novelty postcards can be made in any size and shape.
Arthur - 1996 Postcards from Buster 8-6 was released on: USA: 22 December 2003
The website Postcards offers custom postcard printing. For reference, four 4"x6" custom postcards with glossy fronts cost $3.04 if mailed in bulk. A 5"x7" postcard with similar properties costs $5.04.