Source: Max Kohl A.G. : Physical Apparatus. Price List No. 50, Vols. II and III. Chemnitz, n.d. [1911], p. 1058.

Description on p. 1057:

“Complete Apparatus for Experiments with the Speaking Arc Lamp, F i g u r e on p. 1058,
consisting of:
50,892. Arc Light Hand Regulator (D. C. of at least 80 volts and 10 amps is necessary) 2. 2. 0
63,386. Series Resistance for the Arc Lamp, for connecting to 110–120 Volts 0. 18.0
Or:
63,387. Series Resistance for the Arc Lamp for connecting to 220 volts 2. 0.0
63,388. Self-induction Coil 2.10. 0
63,889. Microphone with Switch and Regulating Resistance 2. 0.0”