With the memory of a million brews etched into the sides: a proper working mug - i approve.
One of the guys on night shift would brew up using an old school tea can - the kind that had a small cup as a lid with enough room for two or three brew ups inside the can. He'd swing it round to mix the tea and milk as he walked back from the water urn while i brought cheese toasties, blackened in a griddle, placed on hot castings coming along the conveyor. Pressure plates were best, as they provided a nice flat surface to toast the bread evenly. V. munchy, especially in Winter.