(Guest post from Chris.)
Shortly before I moved into this house, I decided that my pint Pyrex measuring jug was so constantly in use that I might as well have another for when the first was in the Sisyphean washing-up pile, and went out to the nearest kitchens shop (it was called Kitchens) and bought myself a second pint jug. I assumed, in my folly, that since it had the same function and was made by the same company it would be the same.