Charmion, my decorated Staropramen tankard has the word "pint" embossed on it (I had to search). So that means it should hold a UK pint, which is 568 ml. We Brits will tolerate a half-inch head at the very most in an exact-pint glass.

Bejaysus, I remember supping many a pint of Thwaites Great Northern Bitter at the Ram's Head on Radcliffe Road in Bury. There was so much head on the beer that they served it in oversized pint glasses. It didn't seem right, but hey ho, I could put up wi' it. As you do...