Cytec was purchased by Solvay after 2014. This chemical plant sits in the Ohio River.
More on Willow Island from Wiki
Willow Island is an unincorporated community in Pleasants County, West Virginia, United States. Willow Island is located on the Ohio River at the junction of West Virginia Route 2 and County Highway 10, 3 miles (4.8 km) west-southwest of Belmont.[2] The Pleasants Power Station, site of the 1978 Willow Island disaster, is located in Willow Island.[4] Willow Island was also the location of Cyanamid; later called Cytec Industries, a chemical plant and a large contributor to the Pleasants County school system and area's work force.
I do not know the significance of the date.
I have 2 of the mugs, each in similar condition.
There are imperfections in the glaze, otherwise in good condition as pictured