ID on the English infill plane...
After some googling, I think that this plane is a Henry Slater casting , being finished by a workman, circa end of 19th century. Henry Slater made cast steel plane body for sale to other would be plane makers. Henry and then his son Benjamin made them from 1869 to 1907. And of course they never identified (no markings nor names) these generic castings they were selling to others. This article from Jim Hendricks shows the evolution of this form of coffin smoother. Called coffin, because the sides and/or the back are rounded. It is a very comfortable form to push while planing. The evolution from L-R Pic from above article That would explain this unmarked cast body and the construction details found on this plane, more on this in a minute. The blade could had been any from a number of makers, I don't think that Spear & Jackson made plane per se. Please correct me if I'm wrong... The vendor identified it as a Spear & Jackson Rosewood infill plane Ca 1890 Sheffield As is, ...