Siemens Model 331 "Phonophor Adaptomatic" Transistor (Body)
The Siemens Model 331 (Phonophor Adaptomatic) Transistor Hearing Aid
was manufactured by Siemens A.G. of Germany in 1957. It was a
It measured 2" x 1⅜" x ⅝" thick.
The volume control is on the right side near the top. On the top is a
2-position slider switch (probably the on-off switch).
On the left side towards the back from the battery door is a
3-position slider switch (probably a high, medium, low tone switch).