I am also interested in old cameras. I have seen many in antique stores, but I have only purchased one, recently, that being a Brownie Movie Camera. I thought I would share some of the photos that I have bought from antique stores.
The first images, I recently found and purchased. I believe they are old Stereographs. I took a history of photography class last summer, and these types of photographs are one of the many that we learned about. These stereographs have two images side by side, and were viewed through a stereoscope and produced the illusion of one three-dimensional image.
This first one was by the Keystone View Company, copyright 1901, of The Great Bridge Over the Rhine at Bonn, Germany.
The next one is also by the Keystone View Company, copyright 1905. I've only included one image to show the detail, the card states "Red-hot steel beam from rolling process being cut into lengths by buzz saw, Steel Works, Pittsburgh, Pa., U.S.A.

The last one is by Underwood & Underwood Publishers, copyright 1901. The card states "A beautiful garden avenue in Fairmount Park, Philadelphia, Pa.
This next photo is an example of the old photographs of people that I sometimes buy, depending on how the photograph strikes me. This is a small, square photograph that I saw and had written on the bottom, "Forever Friends". I really like this photograph, even though I have no idea who any of the ladies are in the picture.
Last, the Brownie Movie Camera that I found most recently and purchased. I am really happy to have found this, and plan on buying some 8mm film that I can use in the camera.
I found on YouTube and found a 1957 commercial for the Brownie Movie Camera.