My research has shown this to be an interesting 18th Centuary Worcester 1775 / 1790 tea saucer.   12 cms x 2.5 cms deep. Please use your own sources to verify this item as well.  Early worcester copied japanese items – their back stamps resmbled japanese characters or sometimes a crescent.   This saucer doesnt have a rim as for a modern cup as there is no inner lip.   Very good antique condtion.   No chips or cracks. Please dont hesitate to contact me should you have any queries at all.