This is a late 18th century porcelain Tea Cup and Saucer in pattern 128 by the Derby factory, Circa 1795.
This is a rare Derby pattern that we have not come across or seen previously
The Cup has the Bute shape with a long loop handle and the saucer has a low foot rim. 
Both pieces are hand decorated with gilt rims and have a deep border of a bloom/salmon ground colour with a continuous wavy bend of dark cobalt blue between gilt lines. The outer handle is also hand painted with a gilt pattern. This pattern is number 128 as listed and described on page 292 of John Twitchett's book; Derby Porcelain, 1748-1848, published by The Antique Collectors Club.
Both pieces are fully marked to the base with the crown and crossed batons hand painted in puce, with the pattern number 128 below. The saucer also has an impressed "5" and a painters mark "IV" hand painted in puce by the foot rim.
 
DIMENSIONS
Diameter
5.5 in
Height
2.75 in