SUNRISE Stainless Steel Round Food Ring Kitchen Supply (2 Pieces) (2"D x 1"H)

What "seamless" means here is that they ground it smooth and polished it before packaging. Are these seams ground and polished?

What is the diameter

what is the grade of stainless steel i.e. 18/10, 18/18? and, where are these manufactured?

Could these be used on a flat griddle for cooking eggs?