Pan-American Watercolor Squares by Bertha Corbett, Sunbonnet Sue

Acquired among other Pan American souvenirs, these are the most intriguing.  They are 5" by 6" and say 'Pan-American Souvenir' in the corner.  The opposite corner reads, 'Copyrighted 1900 by Bertha L. Corbett... Minneapolis, Minn.'

These are images of Sunbonnet Kids (Sunbonnet Sue) by the artist who invented them.  It appears they were cut out of white paper, placed on the darker squares, and water colored with details.  One is initialed 'BLC'. 

I can't find anything like them or any original Bertha Corbett art.  The first edition of the Sunbonnet Babies book from 1900 sells for $600 (these were limited to 100 copies).  Still, this is original art of an iconic character by the artist who invented them a couple years before they became popular.  A book published in 1902 is what began the popularity of these faceless children. It's both original antique art and a Pan Am collectible.

I'm very computer literate, I can't find anything like these in any recorded auctions. I can't find any mention of Bertha Corbett having anything to do with the Pan Am expo. It's hard to find any of her artwork at all.  

I'd apprecate any information at all... rarity, value, etc.  I was about to list them on Ebay with some other good Pan Am stuff, but thought I'd better hold off until I learned more and could sell them with better knowledge.

Thank you ALL for your time and consideration.