The Zeiss Ikon Nettar IIB came toward the end of a long series of Nettar medium format cameras, and enjoyed many years of production ranging from 1953 until 1957.
The Nettar line of cameras were designed as the more budget-friendly option to Zeiss Ikon's Ikonta line of folding, medium format cameras. At its heart, the Nettar is a self-erecting, folding medium format camera that uses a direct view viewfinder and a lens mounted in a leaf shutter at the front of the camera. They were found in a variety of 120 formats including 6x4.5, 6x6 and 6x9. The Nettar series was aimed more at the advanced amateur and generally had less expensive lens and shutter combinations. This did not necessarily mean they were built cheaply though as the Nettar actually shared parts with the higher end Ikonta cameras and underwent a number of revisions and innovations.
Zeiss Ikon's headquarters were destroyed during WWII and even after the war ended it took the company time to get back on their feet and get production running smoothly. When they did they updated the Nettar series by releasing the Nettar II 518/16, among other Nettar models. The Nettar 518/16, also known as the Nettar IIB, or Signal Nettar, added a double exposure prevention as its biggest innovation. Early versions of this camera had a red flag placed in the viewfinder that became visible after firing the shutter but before winding the film. This mechanism proved more complicated and costly than Zeiss Ikon cared for so later models of the Nettar IIB replaced this with an indicator window in the top housing of the camera, located behind the shutter button.
Most Nettar IIB cameras are fitted with a 75mm Novar-Anastigmat lens. The maximum aperture varied between f3.5, 4.5 or 6.3 depending on the shutter. That list of shutters includes (in order of rough desirability):
Vario (shutter speeds: 25, 75, 200, Bulb)
Vero (25, 50, 100, 200, Bulb)
Velio (10, 25, 50, 100, 200, Bulb)
Pronto (25, 50, 100, 200, Bulb and self-timer)
Prontor-S (1, 2, 5, 10, 25, 50, 100, 250 or 300, Bulb and self-timer)
Prontor-SV (1, 2, 5, 10, 25, 50, 100, 250 or 300, Bulb, self-timer and M/X flash sync)