I worked at McDonald's in the 80s when they switched over to vegetable oil. The original beef tallow fryer oil was called Formula 47. It came in boxes as it wa

I worked at McDonald's in the 80s when they switched over to vegetable oil. The original beef tallow fryer oil was called Formula 47. It came in boxes as it was solid at room temperature; one box would basically fill an empty fryer. Whole potatoes were not processed in store at that time. The fries came already cut and frozen, and were cooked frozen. As such, nobody at the store really knew the recipe. You filled a basket with frozen fries, dropped it into the fryer, hit a timer button, and in about 3 or 4 minutes they were done. They were dumped into a holding station and salted with ordinary table salt. They could sit in the holding station for up to 10 minutes before they were supposed to be thrown away. I did watch a training video about how they were produced, which involved (as I recall) selecting potatoes of a specific size and moisture content specification, cutting, rinsing, blanching, then flash-freezing.