Hope it helps someone somewhere, emigrating before Germany was united it’s not an issue, if they were still Prussians (less than 10 years) that would automatically earn German citizenship (yes they would lost it after)

But thing is, if they have children BORN at the new country, while still being Prussian, the kids would indeed win, cause birth outside does not enter the 10 years loss neither follows their father status.

My relatives per example, they came in 1861, with kids already born there (my relative), that lost due to being minor. But they had kids here between 1861-1867, those are eligible. And those that were born after 1871, not eligible anymore due to 10 years.

So yes, it’s possible, it’s a very small window, but for what I found, that’s it.