Ernemann had used the name Bob on their folding rollfilm cameras from about 1910 until the Zeiss merger in 1926. Over the years they had roughly a dozen different models, including stereo. Some of the models that were in production were badged with the Zeiss name, but they were just remaining stock from before the merger.
Around 1934 Zeiss introduced the Bob line of less expensive rollfilm cameras. The 510 and 510/2 were marketed in England as Nettar 510 and 510/2. Eventually the Bob name was dropped, and they were known as Nettar everywhere. Some of these cameras are marked Bob, but they are identical in construction to the Nettars.