Yup, full size. Folded only once horizontally, they are usually folded twice.
As to its use, bearing in mind I have only now come across it, and am myself of such a vintage that I saw Octopussy in the cinemas, and so saw the posters used for display, I can honestly not say.
One can surmise based on the similar Seiko posters, and I guess they were used for theatre use. But I never saw any of those either; then again, conscious awareness came later '79.