That basically looks like a smaller version of my Fusin motor,
shown opened up here:
https://endless-sphere.com/forums/viewtopic.php?f=4&t=39877&start=75#p1328934
https://endless-sphere.com/forums/viewtopic.php?f=2&t=80951&p=1328892
which I built a tool to open up out of some old bike frame parts. Mine was splined rather than the four notches, so yours would be easier to build the tool for.
Assuming theyre made by the same people, the same way, then you take all the axle hardware off both sides, then use whatever tool you make to engage those four little indentations around the axle area on the non-brake side cover to rotate the cover counterclockwise, IIRC. (might say in the link above, but I dont remember for sure which way I had to spin mine).
Fusinmotors the company disappeared, but they may ahve made the motors for stuff like your bike before then, or whoever made the motors made them for both companies. Either way, Id bet the same place made them all, because even the font of the writing on teh covers is the same.
