cracked plate?

I HAVE A SERVING PLATE DONT KNOW IF ITS PORCELAIN-GLASS-CERAMIC ETC. IT HAS THE NAME JAPAN WRITTEN ON THE BOTTOM OF THE PLATE NO OTHER MARKS-HOW CAN I RESTORE TO NEW-THEY ARE OLD AND WHEN CLEANED LOOK NEW-YOU CANT BUY THEM TODAY-DOES ANYONE KNOW WHERE I CAN SEND TO MAKE LOOK LIKE NOTHINGS HAPPENED TO THEM-SO THE CRACK WONT SHOW-HELP!