“Our aim is to keep this restroom clean. Your aim will help” (men’s restroom sign)

A jocular sign placed near the urinals in many men’s restrooms is:
 
“Our aim is to keep this restroom clean. Your aim will help.”
 
“Our aim is to keep this place clean: your aim will help” was cited in print in 1970. “Our aim is to keep the toilets clean; your aim will help!” was cited in 1973.
     
   
Google Books
How Many Roads?:
The ‘70s

By Herman A. Estrin and Esther McDonald Lloyd-Jones
Beverly Hills, CA: Glencoe Press
1970
Pg. 159:
THINK SEX is likely to be followed by a lengthy exhortation, “Our aim is to keep this place clean: your aim will help,” or this written philosophic acceptance, found on the John wall of a Westport, Conn., suburban station.
   
Google Books
The Kikuchi Diary: Chronicle from an American Concentration Camp
The Tanforan journals of Charles Kikuchi

By Charles Kikuchi
Edited by John Modell
Urbana, IL: Univiversity of Illinois Press
1973
Pg. 77:
Typical Nisei humor: “Our aim is to keep the toilets clean; your aim will help!”
   
Google Books
It’s Time to Retire When—
By Herbert I. Kavet and Martin Riskin
Watertown, MA: Ivory Tower Pub. Co.
1983
Pg. ?:
Our Aim Is To Keep This Bathroom Clean, Your Aim Will Help.
 
Google Books
The Burning Lake
By Jon M. Thurley
London: Bodley Head
1985
Pg. 105:
Under the cistern some wag had written: ‘Our aim is to keep this place clean, your aim helps’, and another legend read, ‘The management should provide the users of these facilities with braille fly-buttons.’
 
Google Books
Coopers Crossing
By Jennifer Crane
Lulu.com
2009
Pg. 240:
Cheryl was in Muddy’s bathroom reading the “Our Aim Is To Keep This Place Clean - Your Aim Will Help!” sign when she heard Barbi giggling like she always did when she was doing something bad.
 
Twitter
nigel koay
‏@Nigeellkooaayy
Our aim is to keep the restroom clean gentleman! Your aim will help! (Pic taken at neighbourhood cafe)
6:30 PM - 21 Feb 2014
 
Twitter
Judah & the Lion
‏@judahandthelion
“Our aim is to keep this bathroom clean. Your aim would help.” -men’s restroom
1:02 PM - 6 Jul 2014