Let Me Overthink About It Coffee Mug
Because the only thing you need to overthink is your coffee order.
Enamel-coated steel. They are heavy (for enamelware mugs-- still lighter than ceramic), smooth, wonderful to drink from, and crazy sturdy. You can abuse the heck out of them.
Be prepared for some small imperfections. Mugs may have small flaws and variations in the enamel coating which are intended to add to individual character and vintage patina of your mug.