Philco Mark I Transistor (Body) Hearing Aid The Philco Mark I was the first of two transistor body aids made by Philco of Philadelphia, PA. The Mark I was first produced in 1955. Philco manufactured these hearing aids for Montgomery-Ward Co. under the Philco trade name. This hearing aid was quite small for the time and measured 1¾" x 1⅝" x ½" and weighed 1¼ oz. without the battery. It had a chrome case and contained 3 transistors. The microphone sits behind the 4 "star bursts" grill (lower left front). Based on Patent No. 3030586 filed in 1955 and issued in 1962. |  | Click picture for larger view | | | | | |
| Top view of the Philco Mark I showing the on-off/1-6 position volume control (left), the receiver cord jack (center) and the two-position (High-Low) tone control (right). |  | Click picture for larger view | | |
| This hearing aid had a somewhat unusual plug for the receiver cord. Instead of the two pin plug that was common (and used at the receiver end), it used what looks like a standard audio plug, but it is slightly bigger—just a bit over ⅛" in diameter. |  | Click picture for larger view | | | |
| The back of the Philco Mark I. The control functions are engraved on the back of the case behind the controls to which they refer. |  | Click picture for larger view | | | |
| The battery door on the Philco Mark I swung up and to the right from the bottom right corner. This hearing aid used a 625 battery. The clip across the front of the hearing aid could be used as a tie clip with the hearing aid itself hidden under the tie. (One wonders how well the microphone would pick up sounds with the tie covering the microphone grill.)
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