DIS numbers has been a source of endless discussions due to the lack of officially published lists. These numbers consist of a letter followed by a number like e.g. the F.6 mount. To further add to the confusion it seems that there was internal confusion regarding the naming of products as well.
This mount pictured below is mentioned as F.6 in a brochure from 1936 (see blog post here).
According to a more recent source from approximately 1968, the F.6 mount refers to a “light mg tripod” whereas the F.8 is a machine cannon, 20 mm tripod. It must be concluded that there are still a lot to research and that we will continue to explore the Madsen mounts.