I have a glass plate with that slogan moulded into it: an old piece of Gladstone merchandising. It bears out the point made in this BBC audio slideshow, which they should have held for December 29, his 200th birthday.
The unnamed house is Hawarden Castle in Flintshire. Present occupant Sir William Gladstone, great-grandson. St Deiniol’s Library is nearby.
Having just googled this plate, it seems that it was made in 1869 to celebrate Gladstone’s election victory in the previous year, when he became prime minister for the first time.
This piece offers two theories on the meaning of “for the million”. The Irish one less convincing than the other. I had always assumed that it was just an old-fashioned collective noun.
Image from web.