Be aware that the ice cream companies cannot just whip a bunch of air into the product to save themselves money. At least in Michigan, where my dad ran an Ice cream company his whole life and I worked there from the time I was able to take directions reliably until I graduated from college, the gallon of ice cream must weigh a certain amount (air) and that weight is constantly monitored as the cartons or containers are being filled at the freezer. Every 15 minutes or so a gallon is weighed and if necessary the air volume is changed right then as the ice cream continues to be put in the cartons. We used to run three or four freezers at a time when filling quarts and also the 3 gallon tubs.
I suspect that most states have regulations similar to Michigans when it come to the weight of ice cream cartons. You are certainly right on the size however! It is difficult to find a full half gallon now. :M
By the way, the name of the ice cream company was Wesleys Ice Cream Co. and was located in Detroit, Mi. My dad helped form that company from the Ebling Creamery Co. and was still there when it was sold to another dairy in Michigan many years later. He then left and went to the Baskin Robbins plant in Ann Arbor where he finished his career.
Thanks for the opportunity to reminisce! :)
Barney