Since the number is written in the space where the patent number should be,,it is likely the factory style number !! It is 563 and either a check mark (most likely) or a V (doubtful) !! Could be 1920`s or earlier !! Will know more when I can track down the correct Central Glass Co. There was more than one !! Either gesso or plaster on wood base !! My Grandmother had one similar !! Slightly different etch pattern though !!