That term was used with the 4.2 inch motar, also called the 107mm.I've herd the booster charges referred to as "cheese" but never saw a picture of it. Thanks!
The 4.2 inch mortar used a completely different type of charge. It was sheets of propellant about the size of a slice of American cheese, hence the name. The color, if I remember right was a dark olive color. They were flexible and about the thickness of business card. They were sewed together on one end and a full charge was 42 sheets. You ripped off what you didn't need. Once you got below a certain charge you removed the lower of the two part extension on the bottom of the 4.2 inch round. The 4.2 motars we used were made by the Whirlpool corporation and had the trademark symbol on the base plate. The 4.2 looked like a artillery round with a straight two-part extension on the base and no fins since the barrel was rifled.