This is one of those "reverse image" phenomenons that can be revealed when a neighboring building is torn down. In this case, a 1915 building on the corner of SW 13th and Washington bore the sign "Fisher's (Blend's Mah Friend)." A building was erected in 1923 that butted up against the sign to the north. Years of direct contact with the painted sign transferred a reverse ghost image to the adjacent building. When the original building, with sign, was demolished in 2007, the reverse ghost remained.
Fisher's Blend Flour once advertised with the caricature of a black baker proclaiming, "Blend's Mah Friend."
On the west end of the wall, "Ward Buick" is visible, apparently advertising a Buick dealership that once did business there.
The 22-story 12th and Washington project is being built on the south side of the block and will cover this sign forever. Now's the time to get down and see it.