This paper also specifies Van Nuys (about halfway down the page)...
http://www.dailynews.com/centennial/ci_16423843
ETA: It occurred to me that I read a post at the San Fernando Valley Relics FB page recently that discussed Sherman Way at the same time period of your photo, GW. To quote from Keith Mullins on May 4th (on a thread started on May 3rd): "Sherman Way started in the former town of Owensmouth (now Canoga Park) and proceeded east to what is now called Van Nuys blvd, then turned southward to what is now Chandler, then turned east again and ended at San Fernando rd. There was a train rail that ran down the center of it. I used to have a map of SFV, dated 1909, that I found in an attic of an old house near Sherman Way & Reseda. I donated it to the museum at Andres Pico Adobe about 20 years ago. Alot of the major streets had different names. Roscoe was called Sixth St." I also looked in NewspaperArchive.com and found several ads for the Johnston Organ & Piano Manufacturing Co. that note it being on "South Sherman Way" (no address number, however). You might want to post the photo on their FB page, since it is very active and members seem to love solving puzzles about locations in the SFV. Here's the link to the page:
http://www.facebook.com/valleyrelics?filter=3