A few minutes in Google yielded a 1907 SF directory listing the Richardson Brothers as general agents for the Cary Safe Company, business address 131 5th in San Francisco. Even with a telephone number, in 1907!
The Cary Safe Company, of Rochester and/or Buffalo, NY, was in business very roughly between 1893 or earlier, to 1922 and possibly later. They seem to be rather common safes so there is a slight chance you could find another and “junk” it just to get the boltwork and lock. But you’d have to do some legwork to find one. Or establish a “favorite” search on eBay!
David Hewes, among other things, had the idea of using a golden spike to join the first transcontinental railroad and presented the spike which was used at Promontory Summit. The Hewes family had a copy of the spike, made at the same time as the original, and in 2005 donated it to the California State Railroad Museum. This might be a way to contact the family. However, the safe’s inscription might mean that it was one of many sold for use in the building and probably was not David’s personal safe.
