I think the creature on the dagger ia a Wyvern.
http://en.wikipedia.org/wiki/Wyvern
Like the Green Man a pan European thing. I can add pictures of Swiss/German contempory Green Man masks from mountian regions. They might have different names but the same thing. It stricks me as just a little too showy to be British.
Swiss festival mask. Rather like the traditional garb of the leader of an English Morris group. Ancient roots but nothing to do with the so called neo-pagans hotch potch.