What you are showing is a bellows and a focusing rail For a 35 mm single lens reflex camera. Units like this were popular in the 1970s and 1980s for high magnification photography. The camera lens or an enlarger lens is mounted on the front of the bellows, and the focusing rail allows you to use various degrees of extension. Think of it as it continuously adjustable set of extension tubes!
Oftentimes these were used to make duplicate 35mm slides, and Nikon used to call these by various model numbers beginning with the prefix PB
It's a bellows used for macro (extreme close focus) photography. A lens fits on the mount end shown open in the photo and the camera attaches to the end shown capped in the photo. I'd date it from the latter 1/4 of the 20th century -- probably sold for use with a 35mm film SLR.
It also depends on the mount.
Minolta and Canon are quite common along with Pentax. Others are a bit rarer and have slightly higher value IF the bellows are in good shape.
Most likely Leicaflex mount see the second picture with the locking pin. Also Exacta never had internal stop down control which can be done with a dual cable release or the manual lever on thse bellows. The makers name is also a big clue
I have some Leitz catalogues somehere that may contain these bellows of more likely in "The Leica Way" book.