This is a sword Chape based on one depicted in a carving from Eberston, England. A similar Chape (with a bird motif) exists in a copper alloy find from Hedeby (Haithabu).
It measures 51mm x 13mm x 90mm on the inside and has a wall thickness of no less than 1.5mm. If you want a different scale, let me know and I'll try scaling it for you.
The carving and illustration of the carving can be seen at the end of this article, which I highly recommend:
http://sagy.vikingove.cz/bronze-anglo-saxon-sword-pommels/
It's very thin, so you may have troubles casting it, but I've been assured it is possible.