Mid century vintage hobnail pattern cake plate in the hard to find square shape! I'm not sure of the maker, maybe Federal glass?
Color is crystal clear, very little in the way of utensil marks. No chips or damage.
This looks like it was made to hold a metal cake cover dome 10 3/4" x 10 3/4". Plate measures 12 1/4" x 12 1/4" across the rim.