I can’t help with value, but a big factor would be the door. You mention there is no known combination, but the image suggests the door is open? If it’s locked shut with no combo that would really drop the value but if the door is locked open, it’s not a big deal to determine the combination.
My notes suggest Hall’s Safe and Lock started in 1845. In 1896 they merged with two other companies to form Herring-Hall-Marvin. But this safe is Hall’s Safe Company, formed in 1896 by the three Hall brothers formerly associated with Hall’s Safe and Lock. Hall’s Safe Company continued until 1927, so this safe would date from 1896-1927 and maybe somebody else can nail it down better. (Source: American Genius, page 32).