I have a similar latch on one of my doors to the cellar. The little protruding lever with an indentation when depressed, pulls on a rod, and it pulls another rod to lift a bar on the other side out of a metal retainer. Mine is an interior door and has no keyholes. I've always just called it a thumb latch, and I think it's the proper name. Mine is quite older, the house is 200 years old and some sources say those made in the era mine were seldom had key holes, made of wrought iron and went out of favour around 1820 when rim locks began to be mass produced. Decorative ones like yours became popular again around 1870s.

And my particular style is referred to as a gate latch.

Perhaps I am just not seeing the picture clearly, but it looks to me as though you are missing a door handle whose spindle would go through the upper most hole. And I was thinking the little thumb piece would serve as a mechanism to prevent the door knob from turning and thus opening the door. (Kind of like a modern privacy-set in a bathroom.) Is that correct? I've never seen anything quite like it.

To me it looks contemporary to a turn of the century, the 19th-20th c, which sounds like the age of your house. I have a book on older hardware (mostly 19th c, and leaning more towards post Civil War) that I will try and winkle out later this week and see if I can offer more info.

Meanwhile, have you taken the hardware off and looked for manufacturer and/or patent numbers? With a patent number you can use Pat. Off. files (which are online) and sometimes turn up good dates.

The other thing to keep in mind is that sometimes doors were recycled from earlier buildings. I have several (all matching and all installed in lesser or service area postions)from the early 19th c in my building which was created a two or three decades later. A good clue that you may have recycled doors is to carefully measure and examine the proportions of the rails and stiles and any visible mortice and tenons for evidence the doors were cut down, or otherwise altered to fit new or different door frames.

L

There was a type of door lock where the knobs were permanently attached to the plates and a shaft from either side would engage the latching mechanism. I have heard them referred to as "Niles patent".
Casey

Yes, please.......get another view of it, perhaps from a slightly different angle.

I will take a few more pictures as soon as I can. I have puzzled about the top hole, myself. This is mounted on a regular mortise, as were all of the others in the house. The latch that you see actually operates the mortise in the same manner as turning a knob. The door has been recycled from another area in the house. I am quite sure this pantry was added during the remodel that occurred about ten years after the house was built. I am pretty sure the door is original to the house. There are a few others still in place that are definitely original. Over the course of the last year I have come to realize that the house was originally built with more ornate hardware and woodwork. The family that purchased the house about ten years later remodeled and added on. I appreciate all of the responses!

Hi,
I think I found it, It is Gilbert's Patent door lock set.
Here's a link to a very similar lock, with the extra little lever on the side.
Casey

Here is a link that might be useful: antique hardware

That sure looks like it's a hit, Casey!

Just a little follow up: My son removed it and it is Gilbert and patented in 1876. Did a little research and discovered they made locks through the 1870s for a bit more than a decade. I am pretty sure my house isn't quite that old. All square nails and plenty of subtle evidence of a modernization in 1910 or so. All of the doors are proportioned correctly and some even seem to have been specifically made for certain areas. Just when I thought I had it figured out!