Notes: "The ""N"" in N4236 appears to mean ""New"", as in new design but same function. This is still a fixed length planimeter, but it adopts the covered mechanism of the 620000 series that would come later. The advantages of the covered mechanism are that it stays dust-free, and the plastic wheel that sticks through the top covers allows the user to zero the planimeter without touching the tracing wheel and getting finger oil on it. "
