What the ratings mean for your BOM
The 1.5KE12CA_R2_00001: The 10.2 V reverse standoff is the maximum DC or peak-AC voltage the diode can hold without conducting — a 12 V nominal rail with 5 % tolerance sits at 12.6 V, which is above the standoff, so this part is not a fit for a 12 V bus unless the rail is regulated below 10.2 V. The 11.4 V minimum breakdown voltage confirms the avalanche starts at 11.4 V, so the part begins clamping just above the standoff.
Obsolete — sourcing through independent channels
Panjit has marked the 1.5KE12CA_R2_00001 as obsolete. The part is available through independent surplus and broker channels; each lot is verified for authenticity and tested to the original datasheet parameters before shipment.