Thanks much for the catalog, Jack!
Interestingly, it list the handset for the Type 60 as being a Type 41. But then, the Type 60 listed in that catalog has the AE40/50 circuit, going by the induction coil number. So this is indeed the "civilian" version of the Type 60, which did not need a special handset.
For the railway system, the Type 25 handset is incompatible, because it has the wrong push button. The Type 25 has a push-to-listen, release-to-talk button, which places a short across the transmitter when pushed. You can't have that in the L-658 railroad version. That requires to complete (close) the transmitter circuit with the transmitter and place a resistor in the receiver circuit. If a Type 25 handset were used, it would create a short circuit discharging the battery directly across the induction coil, with has only a couple ohms resistance and would kill the battery in short time. In addition, the battery has a very low internal resistance of less than an 1 ohm likely, so it would short circuit the induction coil and withdraw audio-frequency energy from the speech circuit, achieving the opposite of the intended effect.
