I know what you are talking about. My dad's uncle had them on every door of his house except the front and back door.
I believe he had them specially made by a black smith. I'd ask him but the poor man died several years ago.

Twisted, it's amazing what a google search can turn up with the right wording, i.e.: 'door thumb latch'. :)
Here is an entry from my very first page of results.

Here is a link that might be useful: Thumb latches

Check with Ball & Ball. Expensive, but beautiful reproductions.

Thanks, antiquesilver they *do* have nice stuff! Columbusguy, I have searched bing several different ways to try to find what I am looking for. I guess I really don't know exactly what they look like dissassembled. Maybe that is why I'm having such a hard time. I want a latch that operates from both sides, I see thumb latches and gate latches, but have only come across one that is operable from both sides.

Here is another link--this may be closer to what you want.

Here is a link that might be useful: Passage Door Latch

Hi,
In addition to suffolk/thumb latches, there's a lesser-seen latch that uses knobs but isn't any kind of box lock, because it's earlier, and all the works are flat metal exposed on one side of the door. I found a set of them on ebay to give an idea what they look like.
Casey

Here is a link that might be useful: ebay; earliest knob latches