Its known that Mauser did sell/market their products in Japan and the private purchase of pistols occurred. Most examples are not marked in any way and often the only way to connect a Mauser pistol to Japanese use is by bring back papers or provenance of a pistol to a Japanese holster. There are some that are marked but I have never seen consistent markings so there is no claim to all being marked in the same way. The holster with this pistol does appear to be of Japanese style, though there are not enough views of it for me to be certain. I have not see another pistol with similar markings.
Regards,