The relative age of the buildings in this part of DC can generally be determined by how ornate or detailed their stonework is. Even though architects go to great lengths to mimic the style of surrounding structures, rarely do they have the same level of artisanship as their predecessors. I work in one of the older buildings in the area and each window on the first floor is surmounted by a face like this. They alternate, male and female, and they are all slightly different.
I often wonder who they represent.