This appears to be a home hobbyist version of The Thunderbird mug with a flat bottom and no markings of any sort. It features a shiny dark brown glaze outside with an off-white glaze inside. The mold lines are prominent.

The original mug was made for The Thunderbird Hotel in Bloomington, Minnesota, by Red Wing Pottery sometime between 1964 and 1967. It features the words "The Thunderbird" in raised letters on the bottom and shows two birds above a beaver, mimicking the iconic Thunderbird Hotel totem pole road sign. No Red Wing mark appears on the item.