The MMSZ4712 from Micro Commercial Components is a Zener Diode with Zener Voltage 28 to 29.4 V, Zener Current 50 mA(zener test current), Voltage Forward 0.95 V, Current Reverse Leakage Current:- 0.01 uA, Power 500 mW. More details for MMSZ4712 can be seen below.