Boker as a brand has pretty rich history making knives in Solingen. My guess is that they get other companies to make the stones and just put their own branding on. It shouldn't be like a really bad stone, I'm guessing they'd be pretty selective of who the partner with.

I agree with the other comments though, 2000/5000 could be really slow. Don't quote me on this: I think I read somewhere that steel with large carbides e.g. SLD don't fare so well on high grit stones because the fine texture of the stone will rip the carbides out, whereas something like White #1 that's pretty much just carbon and iron will polish beautifully on a high grit. Couldn't find the source on that so I'm actually hoping someone can tell me if I'm right or wrong.

One last thing, if you're cutting something like a tomato or a bell pepper, a toothier edge might be better as it can bite into the skin, whereas a super polished edge might actually slip.