John k & Chilli,
I didn't find any specific mention of the notches in the wrench shank in my search. But I did notice that one of the De Laval wrenches had no notch and another De Laval wrench had only one notch. My wrench, the Economy King, had two notches that were of different widths. So, it's not entirely clear what the function of the notches were/are, but these differences in the notches could likely be explained by dates and brands of the separators involved. One thing is clear, at some period of time, there were a lot of competing separators and wrenches out there. Some were much larger and likely aimed at commercial users, while others were much smaller and aimed at farm/household users.
The only direct knowledge of cream separators I have comes from my experience as a child. When I was growing up, milk companies delivered orange juice, milk, eggs, and cheese to each subscribing household. The milk (whole, non-homogenized) came in glass bottles and the cream was always floating at the top of the bottle. To separate the cream, we just dipped a special spoon/ladle into the bottle, separated the cream layer from the milk, and poured it in a cream server. It was that simple... but it was a long time ago. I can still hear the clinking of bottles on the back porch when the milk man made his morning delivery to our house.
