This stoneware tankard, in really good condition with only a single hairline crack is stamped with the capacity and verification marks required on all tankards after 1836. From these you can tell it is a PINT and was verified as such in the reign of one of the Georges by the relevant local authority.
I think this one is from London County Council and so would guess it is a Doulton & Lambeth tankard, possibly made in Staffordshire. However, if you want to give dad something to do on Father's Day, the definitive text on the subject can now be found online; Marks & Marking of Weights & Measures of the British Isles by Carl Ricketts with John Douglas. Hours of fun can be had tracking down exactly where the tankard was made and verified for use.
You can drink your real ale from a little piece of history.
And as if that wasn't enough I've another little piece of history for sale with a Ceramic Bottle from R. Whites.