This is a Hazel Atlas Crinoline, aka Ripple, milk glass cup and saucer made during the early 1950s. The saucer has a blue piecrust edge while the cup has a beaded handle and has a blue fired-on exterior finish. I would characterize the blue as a turquoise tone, very 50s. I have four of these sets (price is for one cup and saucer only) and all in excellent condition with no chips, cracks or wear - these look unused.
Nice addition to a retro kitchen decor and a very pretty pattern!