This appears to be a lid for a Victorian small or child's chamber pot. It is 5 1/2" across with an inner rim of 4 1/2". The pottery is of the style made by both British and American potteries in the 1800's.
The lid is off white creamware with a raised design at the edges and a transferware decoration of thistles. Perhaps it was meant for those of us with Scottish heritage?
Chamberpot lids make an interesting decoration for your bathroom, and can be displayed on a shelf or hung on the wall. This one has no chips or cracks, but does have overall light crazing without stain.