Plug type in polished wooden box with hinged lid and panel printed with circuit connections. Three pairs of ratio arms are each 10, 100, 1000Ω and resistance arms contains 16 coils from 1 to 5000Ω with infinity plug. Coils with double silk covered are wound noninductively and have a negligible temperature co-efficient. Two spring keys having special contact for battery and galvanometer fitted. Accuracy of coils 100 to 500Ω ± 0.05% and of the resistance coils ± 0.1%.