Is this is a good deal or wot?

I've just come back from a pub lunch at Walter Mittys. Yes, there really is a pub in Oxford called that. But anyway, when I ordered my pint of Ruddles County, the barmaid posed the cryptic question, "You haven't got a Jubilee card yet, have you?". Having established that I hadn't, she handed me a card bearing the following legend....

JUBILATION ALE
Raise a FREEglass this summer & ensure your celebrations go with a swing.

Each time you buy a pint of Jubilation Ale or any other Greene KIng cask ale (Greene King IPA, Abbot Ale, Ruddles County or Old Speckled Hen) you will be given a token. Attach six of these on the reverse of this card and once you have collected six tokens, present it at the bar to receive a unique commemorative Golden Jubilee pint glass.

I ask again...is this a good deal or wot???????