Iloca stereo camera production started with the European (or 7p) format. However, the company soon made the change to the Realist (or 5p) format with the introduction of the Iloca Stereo II, and continued with this format in various guises until production of their stereo cameras ended in the late 1950's.
The earlier European (7p) format cameras were based directly on the Iloca I single lens equivalent, complete with bottom film loading arrangement. This can be a tricky procedure to ensure that the film is correctly located on the film sprockets. Later models had removable camera backs which simplified the loading process considerably. Early models seem to have gained a reputation for being somewhat problematic, no doubt due to the film loading and film transport mechanism - whether such a reputation is deserved or not is open to debate. However, in my experience, the Realist (5p) format cameras from the Iloca Stereo II onwards seem to be quite robust and reliable .
In addition to the list above, there were many variants produced under different brand names such as Realist (the David White Company), Tower (Sears, Roebuck and Co.), and Photrix (Montgomery Ward).
Stereo photography can be fun, and it offers a unique viewing experience, even when using technology from the 1950's. It is remarkable when you consider that this type of equipment was readily available around 60 years ago (in fact dedicated stereo cameras and viewers have existed for around a century and a half), given that 3D photography has only recently started to make a resurgence in today's marketplace with the latest digital technology.