6cm (2.5in) tall, 8.5cm (almost 3.5in) diameter at the rim.
I bought it from a charity shop and improved it. It’s a bit like the way I draw on photographs, except I drew on a mug instead. This one is a bit vintage, with faded gold around the rim. Please note the discolouration in the last photograph, where (I think) the handle has been expertly reattached. I’ve also photographed the mark on the base, in case that’s useful.
I drew on the mug with porcelain pens, so the added markings are dishwasher safe, though I think this mug probably isn’t dishwasher safe because of the gold around the rim. (I’m not 100% sure though.)
Edit: Sold! Oh, I am going to be sad to see this lovely thing go!
Edit again (July 2016): It feels weird to change a post about a past art piece, somehow. But I wanted to let you know that the Stalker and the Stalker’s Cat have been renamed to the Reporter and the Reporter’s Cat.