The porcelain knob is original, riveted on. In fact, I don't think I've ever seen a Selden & Griswold, Erie, or Griswold tea kettle, other than a toy, without a porcelain or wood knob. The spout damage is unfortunate, but the piece is old enough and rare enough to be worth holding onto or passing down. While not the same exact markings, the blue book declines to put a dollar value on the similar one it shows, only assessing it as "rare".