Imperial is not a manufacturer. Imperial Toy Company, previously out of the L.A. area, is a packager of marbles. Back in the late 70's & early 80's, they packaged Vacor marbles. Then, they found cheaper marbles in Asia, like the ones you posted, and started buying them. As we don't know manufacturers names from Asia, the collecting community starting calling these marbles, generically, Imperial. Here are a few bags/package pics.