The MMSZ4686 from Micro Commercial Components is a Zener Diode with Zener Voltage 3.9 to 4.095 V, Zener Current 50 mA(zener test current), Voltage Forward 0.95 V, Current Reverse Leakage Current:- 5 uA, Power 500 mW. More details for MMSZ4686 can be seen below.