Vintage Federal FEG9 Milk Glass Tavern Mugs

Vintage Federal FEG9 Milk Glass Pub Tavern Beer Stein Tankard Mugs Set Of 4 No chips cracks or nicks, on one mug there appears to be a discrepancy in the glass, I cannot tell if this is made into the glass, a bubble or an indentation refer to photos. It is not sharp like a nick or chip. Each mug Measures 6 inches high 3 inches wide 4 7 /8 inches deep Each mug has two men being served pints of ale/ beer by the tavern keeper