This sign has had at least three messages that I can determine. The most obvious is to the left side where "Plate and Window Glass - Framed Mirrors" takes up one square area. Across the top, the messages are a little more muddled. I can make out "Glass Co.," "Service Batteries," and the cities "Seattle - Oakland - Fresno" are also visible. An old photo showed that this was once home to the "Bekins Van & Storage Co."
The building was originally a three story warehouse. Conversion to the Flanders Lofts damaged the sign when windows and doors were cut in the walls, but the sign has not deteriorated much over the last ten years.
You can see this sign from NW Broadway at Flanders and between Flanders and Glisan.