This is a vintage porcelain demitasse cup and saucer in solid royal blue with a white interior and back. Both pieces are marked JLB Made in Czecho-Slovakia. This mark was used by a US importer named JLB&S, also frequently called White Block. They have an art deco style with concentric rings. The cup is 3" x 2," the saucer is 5" wide. The cup has a small scalloped foot. Both pieces are in excellent condition with no chips or cracks.
Royal Blue White Porcelain Demitasse Cup Saucer Made in Czechoslovakia