There was an older firm, overlapping in time, Verlag Louis Koch, Bremen. (Address auf der Brake No 20). This was essentially a photographic business producing cabinet cards from around 1870. Early backs are old fashioned in design with a curly LK logo, and list the speciality as Architecture and Landscape. Later backs have yellow and grey decoration in Art Noveau style and a swirly floral logo. This firm also produced postcards, marked Louis Koch Bremen, Photogr, Bremen 1904 (for example) or Verlag v. Louis Koch, Bremen.
The Deutsche Fotothek site shows four photos by Louis Koch Bremen, including a picture of Halberstadt. Halberstadt is a small town over 200 km from Bremen. It seems very likely these firms have a common link.