細節
A boxwood slide-rule by Dollond
with single slide, graduated in inches on each edge -- 24in. long; and a Routledge enginner's two-fold slide rule with brass slide, by Rabone (2)
with single slide, graduated in inches on each edge -- 24in. long; and a Routledge enginner's two-fold slide rule with brass slide, by Rabone (2)