101D is a Western Electric tube, first appeared in 1921. It's a low power triode. 4.5 volt fil @ 1 amp, Plate voltage = 130 @ 7.5 ma, mu 6.2, Gm 1070, Rp 5800, Po 65 mw.
Valuable tube especially if it's tennis ball shaped.
Norm
:any information/specifications/uses on this tube?