Tom, 

Don may be on to something. My gut feeling is that "rubber plane" means "a plane
 that rubs" or possibly "a plane to make something that rubs" rather than "a pla
ne made out of the material called rubber" or "a plane for cutting the material 
called rubber."

A fast check on-line suggested that "rubber" for the material was in use by the 
end of the 18th century (anyone have the OED? I didn't buy it when it was cheap,
 more fool me); however, I suspect that the abbreviated term was still rare in t
he 1840s, and that "caotchouc" or "india rubber" would have been more common. Fu
rthermore, vulcanization was patented only in 1844 and before vulcanization the 
uses for rubber were very limited since it became brittle in moderately cold wea
ther and sticky in moderately warm weather. With so few tools available at the B
ack of Beyond (fair enough, Tom?) I doubt they would have hauled along a special
 plane just for a rare and little-used material.

Tom Conroy
Berkeley

Don Schwartz wrote:
> GGs, The rubber plane precedes the files, suggesting 
it might be an abrasive tool of some sort.<

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