Just above the large tuning dial, the calibration in Kilohertz is projected onto the rectangular ground-glass screen, forming an excellent and accurate vernier sliding scale.  When tested against WWV on 5 mHz and 10 mHz, the unit's accuracy was less than 1 kHz.

Lautstarke = volume

Tonhohe = pitch/tone

Photo by Bruce Culp

Photo by permission of Stg.C.D.V.&T.