Yes, this is likely a pre-Kodak Nagel camera. Dr. August Nagel worked for Zeiss Ikon for a time before leaving on poor terms, as I recall reading. You can see some of Dr. Nagel's work in the Zeiss Ikon Ikonta -- the strut design is similar to what you'll see in some of the Nagel cameras.
You are focusing the camera correctly.
This style of camera was representative of those around 1920. I don't know enough about this model, but it's likely one of the early roll film cameras. It still has the frame finders that are found on cameras from that era.
Lenses on rails were used with plate cameras, and that's why I think this was an early roll-film camera.
Dr. Nagel was affiliated with several camera companies, some bearing his name: Drexler & Nagel; Contessa Industrie Werke August Nagel, Contessa-Nettel Werke A. Nagel and then Nagel Camera Werke (after he left Zeiss Ikon). The last company is the one that Kodak bought and renamed Kodak AG.
Dr. Nagel, of course, designed the Kodak Retina -- one of photography's great cameras. With it, Kodak introduced the daylight-loading 35mm cartridge, which we continue to use today. The daylight loading cartridge brought photography to the masses (always a Kodak goal) and out of the dark -- literally, because before this, Leica and Contax photographers had to preload lengths of cine film into proprietary film cartridges.