In reply to Rog Wilko:
Hi Rog, yes your Zero is most definitely worth something.
It depends on the condition. I sold a pretty battered example with a pitted and worn pick for £100 a couple of years ago. I've got another used Zero which I'm keeping. In nice shiny condition with a good shaft, you're looking at more like £160/£180. If you can find a rarer Climax - a short-handled Chouinard - in good condition, that's more like £300. I have a collection of Chouinard Alpine Hammers - more common, much more affordable and lots of different variations through the years. I met Yvon years ago, but alas it was before I started collecting ice tools so his signature on one remains elusive.