PRIMO-JR 4x4 TLR cameras, using 127 film,  were made around 1958-60. They were made by a pioneering Japanese firm, Tokyo Kogaku Kikai K.K., later known as Tokyo Optical Company, famous as the maker of Topcon brand equipment.

The examples I have seen are very high quality machines with superb f2.8 60mm lenses and excellent Seikosha shutters with speeds from B, 1 to 1/500. They feature a lever winding mechanism that advances film to the next frame and simultaneously cocks the shutter. A covered red window on the back is used to advance the film to the first frame, after which the mechanism automatically advances to each subsequent frame. As with all 4x4 cameras, it yields 12 frames per roll. They were imported into the U.S.A. by Beseler (who sold Topcon products in the U.S.A.) and by the Sawyer company, an Oregon-based importer, for whom they were labeled as the Sawyer's Mark IV.

According to McKeown (McKeown, James M. and Joan C. McKeown's Price Guide to Antique and Classic Cameras, 12th Edition) the camera he calls the "Primo-Jr I" featured a shutter, and had separate speed and aperture settings. A second variation, which McKeown calls the " Primo-Jr II," had a shutter adjusted in Light Values. I believe this is an error. There is no indication of a model number "I" or "II" anywhere on the examples known to me. As well, no example has surfaced of one of these cameras that did not use the LV system. I believe McKeown's source of this mis-information was Sugiyama (Sugiyama, Naoi, and Bullock: The Collector's Guide to Japanese Cameras). 

The Light Value exposure system is very simple. You first determine, using your light meter, the LV setting. An LV setting is simply a number engraved on the shutter which can be any combination of speed and aperture that is correct for the scene you have metered. On an LV shutter, as you move to a different shutter speed, the aperture also changes to keep your exposure constant. It's the same if you change apertures — the shutter changes at the same time.

Shown above is an example of a Primo-Jr (s/n 283553) along with an unusual variation (s/n 250333) that had a built-in, uncoupled selenium light meter reading directly in Light Values. Another example in the Frugal Photographer collection is missing the TOKO logo on the viewfinder hood (s/n 262071). It is shown here: