I believe this 8 ounce jadeite green slag glass measuring cup was made by Summit Art Glass, which went out of business in 2006. Although it's marked with the Westmoreland Glass logo on the bottom, Summit purchased some of their molds in 1984 and didn't always remove the original company's marks.

The one-cup measure has a raised pour spout and is 3-3/4" high by 3 inches diameter at the base. Raised ounce and fractional cup markings are on both sides. In excellent condition with no damage.