The BZT52B51JS from Micro Commercial Components is a Zener Diode with Zener Voltage 49.98 to 52.02 V, Zener Current 0.5 mA, Voltage Forward 0.9 V, Current 5.0 mA, Current Reverse Reverse Leakage Current:- 0.045 uA. More details for BZT52B51JS can be seen below.