Herring & Co Antique safe combination change possible?

I recently purchased an antique safe with a functional dial combination lock.

I would like to know if the combination for this lock is fixed or can it be changed?
Mfg: Herring & Company
Lock: John Farrels
(patent July 25 1865)

Is there a maintenance schedule that I should follow for the mechanical linkages/lock/hinges for the safe?

I’d be very surprised if the combination cannot be changed.