I've ridden by this building a million times on the "N" and wonder what it is. It is on Judah at 32nd Avenue.
That sign is illegible. The City records show it is an RH-2 two unit, one story building, with two bathrooms and no baths, built in 1948. Hmmm. However the mailing address is 25 Van Ness Avenue, which is City government offices.
(Edited June 14th, 2008: This is simply a substation.)