CERTIX
medium format 6x9 (120)
The Certix was built by Certo Kamera Werk in Dresden, Germany, during the late 1920s/early 1930s. They did at least two versions of this camera, Certix A and Certix B. (I don't know which version mine is. It doesn't say, which probably means it's the first one.)
The shutter is an ever-ready AGC Vario with speed settings 1/25, 1/50, 1/100, b (bulb) and t (time). The lens is a 105mm Certo Anastigmat "Certar". Focus can be set manually from 2 to 7 meters plus infinity. Aperture can be set from 6.3 to 22.
The Certix is very fun to have, especially next to all the plastic digitals. It's a pain to meter for it, though, as that has to be done completely manually.
The images do come out a little soft, but otherwise it's ok. The light leakage on the left of the first image below was caused by the "back door" not being quite able to shut properly. It was soon fixed, and now the camera works like a charm.