BX-42

According to SIG 5, it is a spare parts box for SCR-245-GX, MX and PX. From the contents listed (one vibrator, two RK-60 rectifier tubes and fifteen fuses, I would assume that it was specifically for the PE-125-AX vibrator power supply. If so, the vibrator would be a VB-5 (don't know why the SIG 5 entry didn't give that and why there is only one). And the RK-60 would have to be a substitute for the VT-249/CK-1006 which is listed as the two rectifier tubes in the PE-125-AX in the manual on the various SCR-245-*X. I haven't been able to confirm that the RK-60 and CK-1006 are interchangeable other than that they have the same basing and similar voltage and output current ratings. But RK-60 is a vacuum rectifier and 1006 is a gas rectifier.