(yes, I know some of you were born in the eighties - sigh)
Each page represented a different letter from the alphabet and your task was to find as many objects beginning with the letter in each piece of art.
I can remember spending hours gazing at each drawing and ticking things off as I found them.
Then when I was having a search on Amazon for books for Christmas for boy*jelly, I came across the "I Spy" books by Scholastic.
(NB - my photos are scans of one-half of a page, so don't go trying to find the things - they may not be on that side of the page!)