Mid century vintage Jackson China plain white ironstone plates - very small, just 5 1/2" in diameter. These are smaller than bread and butter plates - they'd be nice for snacks, a doughnut or a muffin, maybe a slice of pie.
This is a set of six plates all in very good condition, clean and glossy, no marks or finish wear. They'll look cute stacked on your hutch or open shelving, too!