The BZX584B12 from Micro Commercial Components is a Zener Diode with Zener Voltage 11.76 to 12.24 V, Zener Current 5 mA, Voltage Forward 0.9 V, Current 1 mA, Current Reverse Reverse Leakage Current:- 0.1 uA. More details for BZX584B12 can be seen below.