Ran into this awesome bit of old San Francisco on Stephenson Street, between 6th and 7th street in downtown SF. It's apparently a covered walkway advertising the "Weinstein Department Store" on Market Street. Here's the story of this sign, according to foundsf.org:
Spanning Stevenson Street midway between Sixth and Seventh, a covered footbridge connects what used to be Weinstein’s Department Store and the building that served as that company’s office and warehouse space. The department store has been converted into live/work lofts, and the onetime warehouse is now occupied by a dot-com enterprise. I remember when such footbridges were numerous in the back streets of San Francisco, not so very long ago. This is the only one that now remains in the central city.
According to this discussion thread, Weinstein's was a discount department store in San Francisco, started after 1906 and closed in the late 1960s.