Having grown up in California, I have a special interest in pens made there. Especially appealing are those dating back to the 19th century and the Gold Rush era. Not many writing instruments were made on the West Coast back then, as manufacturing was concentrated in the Northeast and Midwest. So this dip pen was a lucky recent find with its gold nib marked "J. H./BAPTIS/S.F./5".
John H. Baptis was a Civil War veteran who made and sold gold nibs in San Francisco from approximately the 1870s through 1900. I've not had time to do a thorough investigation, but in the San Francisco City Directory for 1878 there were but two listings under Gold Pen Manufacturers: Henry D. Pearce at 615 Montgomery, and Baptis at 328 Bush. By the 1880s Baptis was at 319 Kearny, where he appears to have remained as long as he remained in business. The Kearny address appears in the 1899 city directory, but in the October 31, 1900 Insurance Press it is recorded that a life insurance payout had been made for a J. H. Baptis of East Oakland (now Berkeley).
Although the buildings in San Francisco are gone (319 Kearney in particular appears to have been lost in the 1906 earthquake and fire, as the building now on that site was built in 1907) Baptis's 1880 home at 1425 Milvia in Berkeley survives and was recently lovingly restored. You can read about it here.
The plain black hard rubber holder does not appear to be of West Coast manufacture. It is marked "F. M. LIBBY'S PAT. MAR.4.84." This would be US patent 294477 issued to Frederick M. Libby of Portland, Maine. It is a rather unusual design that proposes to add springiness to a nib by allowing it some movement rather than gripping it rigidly.
UPDATE: Baptis appears in the Alameda County record of deaths as entry 267, 22 August 1900. He is recorded as 64 years 11 months and 15 days old, married white male, calculated birthday 7 Sep 1835. Tuberculosis is listed as cause of death; birthplace as New York.