Pyrex Vintage Slate Blue Coffee Mugs Set of 4

Charming vintage Pyrex mugs in slate blue. I think Vintage from maybe 1970’s - 80’s. excellent used condition. No chips. Set of 4 coffee cups. Stamped: PYREX. Microwave safe no stove top or broiler Corning, New York USA. “ And a number either 18, 16, or 56 Ideal for daily use. Solid blue gray color on the outside , white on the inside. Milk glass, durable See photos for more details. Set of four Vintage PYREX