In Germany potatoes do not get as large as ours here do. The family that started/owns The Little Potato company are from The Netherlands. I am assuming that the potatoes in Holland are basically like German ones. About 30 years ago, before we had Yukon Gold potatoes here (At least I didn't know them) I brought a few small German potatoes to Canada, Yes, I lied at the border, because you're not supposed to bring stuff like that into the country. I really liked the small yellow potatoes that they had over there.
I planted them in our garden. The first year they were pretty well the same as the originals that I smuggled in. I kept a few seed potatoes from that year's crop for the next year. The second year they were bigger, and not quite as yellow. The third year they were pretty well the same as regular potatoes here. They lost the yellow colour and the buttery flavour and also the texture was different.
My conclusion was that it had to be the soil and also the climate. So, knowing of my experiment, I think The Little Potato Company has done a tremendous job in being able to bring those small potatoes to market in a big way. Here they are in Costco. I really like them, and I have also seen Fingerlings occasionally here at the farmers' market.