Double slide rule patterned after a development made by S. Coulson, an English engineer. Rule has 2 sliders with same thickness as the rule. Graduated on both faces to create 4 slide-rule calculators on 2 faces. Components of rule are held together by brass plates at ends of both faces.
Inscription/Sig.
"LOFTUS MAKER 321 OXFORD ST LONDON" along one edge of rule.
