This Standard Mica Condenser is listed in the Leeds and Northup Catalogue 10, "Capacitance, Inductance and Magnetic Measurements" from 1927 at $65. It was "subdivided into 5 sections: 0.5, 0.2, 0.2, 0.05, 0.05 microfarad. Connections engraved on hard rubber top plate. Accuracy, .25% for all sections. Mounted in polished mahogany case with cover." The use of knife switches obviated the use of easily-lost plugs, and the reduced mass of metal on the top plate reduced stray capacitances. 

   This apparatus is in the Greenslade Collection.