1201 Evelyn Avenue, Berkeley
This is only the second dated mark by Immel I’ve found.
1606 San Pablo Avenue
William F. Wilson (1839-1912) was once a major name in San Francisco. He was born in Germany, presumably with a different name. According to a laudatory article in the San Francisco Examiner in 1891, Wilson came to California in 1856 and soon made his name in San Francisco as a highly competent provider of plumbing services in large, prestigious building projects. Later he served on the Board of Health but was removed by new mayor P. H. McCarthy in a late-night coup in 1910. He died in 1912, leaving a large estate. His company was liquidated in 1933.

1427 Broadway
I spot-checked Oakland and San Francisco directories plus the newspapers and found nothing whatsoever about this guy.
483 Michigan Avenue, Berkeley
Lincoln Cushing also recorded this date at a nearby address.
I have Apodaca & Huelga marks now from 1995 to 1998, but have found no information whatever about the firm.