The BZM55C4V3 from Micro Commercial Components is a Zener Diode with Zener Voltage 4 to 4.6 V, Zener Current 1.0 mA, Voltage Forward 1.5 V, Current 5.0 mA, Current Reverse Reverse Leakage Current:- 1 - 20 uA. More details for BZM55C4V3 can be seen below.