“A parking meter is a device that enables you to do two hours’ shopping in one”

Parking meters often have a maximum of one hour—otherwise, people would leave their cars longer. “Parking meter — A device that enables you to do two hours’ shopping in one” is a joke that was published in Changing Times: The Kiplinger Magazine in May 1958. “A parking meter is a device that enables you to do two hours’ shopping in one” was printed in the “Today’s Chuckle” feature in many newspapers in 1968.
 
       
Google Books
May 1958, Changing Times: The Kiplinger Magazine, pg. 2, col. 1:
Parking meter — A device that enables you to do two hours’ shopping in one.
 
22 May 1958, Hampton (IA) Chronicle, pg. 4B, col. 2:
The parking meter is the first invention that enables women to do two hours shopping in one.
     
20 September 1959, The State Journal (Lansing, MI), pg. 38, col. 5 ad:
Parking Meter: Urban device that gets you through two hours’ shopping in one.
(“Dines Dictionary,” in an ad for Dines restaurant.—ed.)
 
1 October 1961, Chicago (IL) Daily Tribune, “Radio TV Gag Bag” by Larry Wolters, Chicago Tribune Magazine, pg. 28, col. 3:
Jim Conway: “A parking meter is a device that makes you do two hours shopping in one.”
     
26 August 1968, Arkansas Democrat (Little Rock, AR), “Today’s Chuckle,” pg. 1, col. 1:
A parking meter is a device that enables you to do two hours’ shopping in one.
 
2 September 1968, Chicago (IL) Tribune, “Good Morning.” sec. 2, pg. 5, col. 1:
A parking meter is a device that enables you to do two hours’ shopping in one.
 
25 June 1971, Courier-Post (Camden, NJ), pg. 16, col. 1 ad:         
A parking meter is a device that enables you to do two hours’ shopping in one.
(“Quick Snacks” by Adolph Lubas. Ad for Adolph’s Drive-In.—ed.)
 
Stress Humour & Health (Australia)
Humour Shots Part Nineteen (2006)
(...)
A parking meter is a device that enables you to do two hours shopping in one.