Key Klub 856 Bush Street between Mason and Taylor. This thing is spectacular! The peeling paint, the broken tubing, the real estate ad armature, the clever use of the letter “K”, the inexplicable “Crossroads of the World” tagline. The building dates from 1922; I’m unsure of the sign’s vintage but it’s definitely old.
Check out FoundSF and this great 3D image of the Key Klub circa 1987. The more things change the more they stay the same.
Also, see this cute little account about the Key Klub’s pet rabbit in the October 1954 issue of Life Magazine.