Japanese rectangular vase with frog.

This vase is 6" high x 5" wide x 3" deep and weighs a smidgen over 2 lbs. It has a removable frog, a tiny oval "Japan" label on the base and is signed in front on the lower right corner. The design is incised into the vase and hand painted, almost identically on front and back. The sides are painted a solid blue. It appears to be unused and shows no signs of wear but reminds me pieces from the 1950s-1960s. Odd, but nice piece.

There are several interesting things about this vase. The "Japan" label is the smallest label that I have ever seen on a piece of pottery. I have also never seen a piece signed like this one is. I did find a very similar vase on ebay with an "LJ Japan" foil label and other less similar vases with no frogs with "Lego" labels. It think it is a stretch to link my vase to the "Lego" labeled vases, which I found some information about, but I have no problem at all in concluding that the other vase is made by the same kiln though perhaps not imported by the same importer.

I found about two dozen pieces of LJ marked porcelain on ebay, some not labeled but signed "LJ" in gold paint on the base and some bearing both the foil label and the painted initials. All of it was very nice quality porcelain and hand painted. None of it was also signed like my vase is. I also found a dozen more pieces on Etsy and couple of the pieces were figurals in bisque and one metal plant stand with the foil label. I've started researching the "LJ" trademark, but since most information about the LJ pottery dates it to the 1950s, I am not hopeful that I will find much.

Similar flower/frog vase on ebay:
https://www.ebay.com/itm/Japanese-porcelain-rectangular-hand-painted-vase-with-flower-removable-lid-6-H/123661389196?hash=item1ccacb0d8c:g:e8UAAOSw24hccefU