i looked around some and could not find your exact sign,but i did find an entry of when
the slogan...Drink Coca-Cola in bottles...was first used
Drink Coca-Cola in bottles 1910
http://www.angelfire.com/la/malonewd/index7.html
you might find something in the coke blog
How Much Is My Stuff Worth?
http://www.coca-colaconversations.com/my_weblog/collectibles.html
i looked some in the virtual museum,but didnt see it,cool place though
http://www.theverybestofcocacola.com/
this mans guide/s could prob be found at your local library
Petretti's Coca-Cola Collectibles Price Guide: The Encyclopedia of Coca-Cola Collectibles
http://books.google.com/books/about/Petretti_s_Coca_Cola_Collectibles_Price.html?id=yDvifcXRocUC
my moms cuz has the bottle cap sign and an old cooler, with the bottle opener,the last time i saw them
they were in excellent shape,so im guessing from reading up on coke collectables,at auction hers would
go for about 4-500$ for both,maybe more it depends on how much the item is wanted too,so if your
going to auction your sign read up some,so you can get a ballpark idea of its worth