[mikethedruid]

Ron is right, "Dead men tell no tales." I will; however, attempt to give you an answer. The electromagnetic type speakers have an advantage. The field coil can be used as a filter choke in the power supply of the radio, smoothing out the DC, and reducing hum. PM speakers do not have a field coil, and so do not have this advantage. If one wants to provide this inductive smoothing of the DC, one must add a filter choke to the power supply circuit, which takes up space on the chassis, and is another part which costs money. The difference between the cost of an electromagnetic speaker, and a PM speaker in those days was less than the cost of an additional filter choke. So, the choice of using an electromagnetic speaker made sense from both a chassis room and a cost perspective.