How do you tell the year of manufacturing on a milk bottle? I have one that has a 43 on the bottom and an 18 on the heel of the bottle. It is a pint from the Waymart Dairy in PA.
These machine made embossed milks run from about 1910-1940s. You might check the newspapers of the area for possible ads and this would give dates of operation. A lot of family type dairies sold locally and didn't produce much advertising.