This lens is collapsible.

Focal length: 50mm
full format, APS-C equiv. 75mm
Mount: Contax rf, but have a look at the last paragraph
Aperture: F 2.0 - F 22
Min focus distance: 0.90m
Length (see*): 11/22mm [+ 19/25mm for the adapter],
tube protrudes 22mm to the back when collapsed
Diameter: 45mm
Weight: 150gr.

*Contax mount is quite different. In fact it's two mounts. The inner mount has a focussing helical, so the standard lenses don't have one. The outer mount is for other lenses which have their own focussing device. Its difficult to measure. I have taken the locking pin for reference.

Some pictures:

A6000 and the lens, collapsed

A6000 and the lens, extended.

Sample pictures: You may click on the sample image (except closest focus) for full resolution. The full resolution image opens in a new window, so you can keep it open for comparison. Focus is on the satellite dish to the right of the big solar panel near the center of the photo.

F 2.0.

F 8.

F 22.

Closest focus  is 80cm from the outermost edge of the lens, F 8. Focus on the program wheel of the camera.

This is the oldest lens (except large format) that I own. According to the serial numbers lists on the web it's from 1937.
Wide open it's soft, but it's perfectly usable. At F 8 it's sharp. At F 22 it hardly gets blurred due to diffraction, it's better than other lenses. Its contrast is astonishing for an uncoated lens. The lens has no close focussing capablities. It is very small and lightweight, particularly for a F 2 lens. A nice old lens which offers one usable stop more than a standard lens.

This lens is collapsible. There is enough room inside the adapter to collapse it, it doesn't collaps as far as some M39 versions, but you have to act at your own risk. Please proceed slowly, you don't want to aspire dust into the camera. The adapter is difficult to find and sometimes expensive, but Contax mount lenses are often much cheaper than their M39 versions.

The lens can be collapsed into the A6000. Please push cautiously, it collapses into the adapter, but again it's at your risk.