I purchased a used, near-mint PT-50s about five years ago and had it black rhodium plated at the same time. It shows signs of use, but there are no major scratches or shank dents. I recall the plating cost around 20,000 to 25,000 yen at the time, but I don't have a certificate. The plating company told me that the plating is quite hard and cannot be re-plated. Please refer to the images for comparison with a standard silver mouthpiece.