Half glazed Western style Earth and sky Japanese cup

This cup is 3.5" high x 3" diameter, indistinctly marked on the bottom. The first image I saw of this cup made it look like a very interesting yunomi and I was excited to take a closer look at it. Then I saw the second image showing the handle and prepared to just move on, but decided to take another look. The half glaze is very interesting and has an earth(not glazed)/sky(glazed) theme which I found appealing. I liked that it was painted on all sides of the cup, not just on one side, too. I also liked the white swirl in the interior glaze. It came in the original, attractive box in good condition, as well.

The seller purchased it new in Japan circa 1980 and it disappeared into a closet until recently. Though I am not interested in Western style Japanese cups, this one had some unique facets I have not seen before. It had a "make offer" option, so I made an offer of half what the seller was asking since it is not really my thing and they graciously accepted. So now I own a Japanese cup with a handle.

The seller did not know who made this cup and neither do I, so it is also a research opportunity. The packaging suggests that it is not a studio artist piece, so probably made at a kiln. Since it was purchased in Japan and has no English on the label, I think it may have not been made for export. Not sure of the history of the handled cup in Japan....