Top tube is fumed with gold and silver in addition to being wrapped, raked and encased.
All tubing has been encased.
If you look closely at the 3rd piece of tubing you'll notice some haze in the end portion. This is called devitrification. Such is due to being over worked and the elements enter a crystalline state.
Once it's enter this state is can't be reversed, at least to my knowledge it can't.
https://youtu.be/Tkd5A-KDAiQ
https://youtu.be/XHjhAmQMqME
https://youtu.be/_Y4WnJhdVmk
https://youtu.be/xadAtFuksGg
https://youtu.be/u2h-F2VQF24