There is a black dot on the base that must be under the coating when it was produced.  Please see photos.

This vintage white milk glass pitcher and 4 glasses set by Indiana Colony in the Harvest Grape pattern is a charming addition to any home. Made in the United States, the mid-century modern style and matte finish give it a unique and nostalgic look. The set includes a pitcher and 4 glasses, all featuring the classic Harvest Grape pattern on white milk glass, adding an Americana touch to any dining or kitchen décor.