Rare pre-1840 Colonial Period thumb lock Porcelain doorknob/back plate set

When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Rare pre-1840 Colonial Period thumb lock Porcelain doorknob/back plate set:
$88.50

This is a gorgeous entry/pantry door knob and plate assembly with rare thumb locking mechanism.
The knob is porcelain with a brass decorative center. The ferrule and rose along with the thumb latch, are all brass. The back plate looks like eastlake pattern and very Gothic and is made of cast iron.
There are a few minor chips and some staining on the porcelain, but nothing serious.
The back plate measures 5\" my other architectural items i have listed as well.
Thanks for looking!
Here is some history on early colonial doorknob sets:Mortise locks had been made in England since around 1790, but were not largely used in America until 1840s. This was due to the narrow thickness of the doors in the majority of Colonial period houses. Being 1¼” or less, the doors could not be cut out or mortised to accept such locks. These thin doors were usually equipped either with surface mounted thumb latches, spring latches, or rim locks. Then during the1820s/30s, common interior doors started to become thicker (1½”, 1¾”, 2\"), which allowed them to accommodate a mortise lock or latch. The latches pictured are ingenious apparatus invented by the Blake Brothers, nephew of Eli Whitney, of New Britain, Connecticut, which were mortise cylinder latches patented in 1833, using a concept that would not be universally accepted until the 1940s.