Microtone Model 51 "Century" Vacuum Tube Hearing Aid The Microtone Model 51 "Century" was produced by Microtone Co. of St. Paul, MN in 1950. It was a 3 vacuum-tube hearing aid measuring 3" x 2¼" x ¾". It weighed 4¼ oz. without the batteries. The elegant case was gold-colored anodized aluminum. It had a fancy microphone grill on the upper front of the case. The volume control/on-off switch was located near the top on the right side. It was a bit unusual in that it was a wheel that stuck out both in the front and the back. That made it easy to adjust the volume by rolling the wheel between your thumb and index finger. |  | Click picture for larger view | | |   | | | |
| Right side view of the Microtone Model 51 "Century" hearing aid showing the plug on the lower part of the right side. It had two pocket clips—one on each side (right).
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| Rear view of the Microtone Model 51 "Century" showing the volume control wheel (top left) and the 3 miniature vacuum tubes (top left). Both the front and the back of the case were hinged at the bottom and folded down to allow easy access to the inside. |  | Click picture for larger view | | | |
| Close up view of the vacuum tube compartment of the Microtone Model 51 "Century". It used 3 Raytheon vacuum tubes. |  | Click picture for larger view | | | |
| Inside front view of the Microtone Model 51 "Century" hearing aid showing the microphone (top left quadrant), volume control wheel (top right) and the battery compartment (lower two-thirds). The "B" battery went in the upper compartment and the "A" battery at the bottom. |  | Click picture for larger view | | | |
| Rear view of the Microtone Model 51 "Century" showing the volume control wheel sticking through to the back and then name engraved into the lower back "Microtone" and "Century 51". The clip to hold the front and back on is at the top center.
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