Hi Fatboy, I feel as if I'm being rude calling you that.
Your nicely de-rusted tool looks like a concave spokeshave. These are being suggested as useful amongst the windsor chair making community. I think Veritas do one, there may be others. An interesting evening awaits you trawling the web for more information.
A good start may be with a search for 'concave shave', or 'concave spokeshave', via your favourite search engine.
HTH
xy