Vase with unusual mark - Chinese?

This vase has an unusual coating on it. Almost like a glaze? Does anyone know if this is a vase or is it missing a top piece? About 12 inches high. I wanted to clean it but am unsure how or if it will hurt the piece if I do so. It is very pretty. Also, it has an unusual mark on the bottom. Chinese? I don't know how old it is, either. Thank you.