1904 St Louis MO Missouri World Fair Expo glass maze puzzle cardboard backer

Description

This is the 2.75" square cardboard backer from the 1904 World's Fair glass maze puzzle. 'It's up-To-You to do the World's Fair Puzzle' - patented June 29, 1904. Obviously there is no glass here - this is just the cardboard backer. Graphics on the picture "Central Cascade and Festival Hall " and stamped on the corners are 'World's Fair Puzzle" and "St. Louis 1904"
On the reverse is the explanation on how to play (the non-existent) game.
The impression on the front is slightly visible from where the glass maze was. For the record, the person we got this from had it about four decades and they got it without the glass.
If there's a flaw, or flaws, with the puzzle back we're doing our best to explain it and show it. While a flaw (or flaws) may not be mentioned in the text description, it (they) will surely be visible in the photos. Make sure to see all the photos that ebay shows at the top of the auction.
Please do not hesitate to ask questions or to request better pics of something in particular.
Shipping will be USPS First Class. It will be in a zip bag in the package as an extra precaution from the elements.