Mid century modern.
Unused discontinued vintage surplus, no box.
Not 100% sure? please buy one first, I am willing to reserve the amount you need.
Slightly dimpled: sky blue specks on an off white background,
4-3/8" square X 5/16" thick.
Price is for 1 tile.
Great as a repair replacement tile.
MPN 555
From the 1970s
Color 361.
6157-100