There are plenty of old instrument amps out there, mostly matched with lap steels originally, that were equipped with a field coil speaker from Lansing Manufacturing Company. I have seen examples from Rickenbacher, National, Dobro and Schireson, all Los Angeles makers in the 1930s. When National and Dobro merged to form National Dobro Corporation in 1935, they were located for a couple of years at 6920 McKinley Avenue, Los Angeles, directly next door to Lansing's factory at 6900. So it seems that Lansing involvement in professional sound goes back quite a ways!