Hello Thomas,
This is a really good sumara - congrats!
The tin is supposed to be a sign of status, i.e. having taken a head... Unfortunately, tin is not stable and deteriorates sooner or later. Be careful when working on this piece and try to store it with as little fluctuations (humidity, temperature, etc.) as possible.
Here are some good examples:
http://www.vikingsword.com/vb/showthread.php?t=15109
Just in case you get bored with it, give me a call, please.
Regards,
Kai