Hello all:  If you are interested in tracking Mr. Eiler, a possible
1910 Steinway dealer, you might contact the reference desk at the
main branch of the San Francisco Library.  They will likely have an
old "Polk City Directory" of people and businesses from that era.
Polk would reveal the old address and possible officers of the company;
old telephone directories would likely list the same information.
I often track old historical information in this manner.

Only the main branches of city libraries usually save the old Polk City
Directories and telephone directories.  There is also the "Cole's"
Directory that has replaced the defunct Polks, which ceased publication
in the 'eighties, I believe.  Cole doesn't list as much information as
did the old Polks Directory, as Polk used to send representatives door
to door and ask your name, address, telephone number, and occupation.
If you had a business they would also ask about officers of the
company as well.  When people became more private about themselves,
times changed.

Historical societies would be another resource.

Glenn Morris
Portland, Oregon