The patent dates suggest several possible patents, assuming they are for the locks and not the door or boltwork. I wonder if they (manufacturers of the era) used dates, rather than patent numbers, to make it slightly more difficult to look up the patent, or just to impress people with the date?
The 2/1/1870 patent is probably 99,400 which is for the invention of what we now call indirect drive (or outside drive), the driving of the lock’s spindle via gears off-axis from the knob’s spindle.
The 5/23/1871 patent is either 115,230 which is for a zero-change lock (which is supported by the fact the dial rings in the recent photo have only one mark), and/or 115,231 which is for a “clamshell” sort of roller bolt, to thwart picking via micrometers. It’s even possible that both patents apply to these locks, a close-up photo of the bolt end of a lock could clear that up. Or a photo of a lock with the back cover removed.
Jim
