This set includes date plaques, as would typically be cast into concrete structures such as bridges, culverts, and foundations. They may also be used as cornerstones on masonry buildings.
Four of each year from 1920 to 1930 are included in this set. The 8" numerals are modelled from an un-numbered CNR standard drawing, "Standard Instructions for Dating Concrete Structures".
They can easily be fit into a recess in your structure, simply recreating the recessed date lettering.