Sounds asa though your grandparents had the same idea as those friends. A herd of mainly Friesians (I'm not sure what the difference is between them and Holsteins, as they look the same, and people call their black and white cows over here Holsteins now) with a couple of either Guernsey or Jersey to make sure the butter fat was up to the right level for the dairy to accept it. They put the milk into metal churns (which were not used for churning) and took them out to a stand by the farm entrance, from where they were picked up by the dairy lorry, which left empty cleaned churns for the next lot. Then they had to install a tank at the milking parlour and tarmac the track from the road for the dairy tanker. You can still see the old stands by some farms.