Wedgwood china butter pat plate antique Edinburg blue & white aesthetic vintage transferware

Antique china butter pat plate (about 3" in diameter) Wedgwood Edinburg (Edinburgh?) pattern china.

This has roughness and grey spotting to the surface - I can't think what might have caused it, perhaps it was original to the piece?

Somewhat unsightly, but this is a really rare design and butter pats are generally hard to find in the old patterns.