Sumter Telephone Mfg. Co. No. 20 "knurled nut" split shaft desk set

This is the No. 20, Sumter "knurled nut" split shaft. This desk set is the last split shaft design modification made prior to the 1910 introduction of the Sumter utility stand model. Tools were no longer required to remove screws to expose the switches, the top knurled nut could be turned with your fingers.