The one on the left was a CERTO (or similar brand) fruit pectin bottle. You would use it when making jams/jellies to help solidify the texture. The bottle would contain 2 doses of the pectin, and as such you would pour until the line (in your case 1/2 cup). Royal Crown was a fairly big cola name that sold nationwide at one time - check the bottom, it might have a date code depending on the manufacturer.