The History of a San Geronimo Valley Volunteer Fire Department, As of 2018, this appears to be from the Forest Knolls VFD.
"On the back of this photo is written: Old San Geronimo Valley Volunteer Fire Department. Location looks to be in Forest Knolls, San Geronimo Valley, CA. Date unknown." Photo and caption courtesy Senior Captain Greg Jennings, Marin County Fire Department, retired.