Western Electric Compression Driver 30150-B Permanent Magnet Version of 555
Good working order with original diaphragm.
DC resistance of 13.2 ohms.
This is of course the UK sourced version of the well known WE 555/555W high frequency horn driver which is a PM version. The 30150-A was the original unit manufactured and was a nice piece as well but this B type was brought out with a heavier magnet which allowed the company to claim efficiency specifications equal to the field coil version of the 555's. It was the best version made by Western Electric Co.
