19th century door hardware mystery
After removing my home's upstairs interior door hardware to remove the paint on them, I noticed a patent date of 1870 on the back of all the locks (Corbin rim locks). My house was built in 1857, yet the door hardware dates to at least 13 years after that. I don't think they're later additions, because the wood under the hardware is completely bare with no trace of paint or finish, and there are no holes or ghosts of different hardware. I searched every door, and I can't find one trace of previous hardware on either side. I thought it was really odd that someone would have changed all the hardware on all 6 doors such a short time after the house was built. I came up with three possible explanations:
1. The hardware was changed, but door hardware in the 1850s - 1870s was standardized and all exactly the same size with holes in exactly the same places;
2. The upstairs doors weren't added until a while after the house was built (unlikely, since they're consistent with 1850s door construction)
- The build date of my house is wrong (?)
I attached a link of what my hardware looks like. It's identical except for the patent date, which is January 1870.
Anyone have any ideas?