Here are two examples of Book #5 (Three Little Pigs) in this series. The only obvious difference in the covers is the color of the lettering. Between the beginning of this format in 1917 until 1920 the lettering on the cover was either yellow or red. This is an easy was to instantly determine the date published in certain books of this series.

#5 Early edition

#5 Later edition

For more information on Series 186, click here