Notes: "The K&E 4041 is a Mannheim type slide rule and was made from the time before K&E were making their own slide rules until about 1943. K&E offered Mannheim type slide rules from 1883, but the 40xx model numbers weren’t used until 1901. There are several features that help date this rule, but nothing that dates it precisely: the early style metal-framed cursor, no cm scale in the well, no scale identifiers on the face. It dates from 1915 to 1920; although this style of cursor was out of use by then, it may have survived in the case of rules with magnifiers, as it gave a sturdier attachment for the magnifier than the all-glass cursor that followed. "
