The '3126' indicates a straight plug shell style. The 'F' denotes the service class as environmentally sealed with olive drab chromate over cadmium plating. The '12' specifies the shell size. The '-10' refers to the insert arrangement, indicating 10 contacts. The 'P' specifies a pin (male) contact type. Identifies the part as a U.S. Military Standard connector, specifically MIL-DTL-26482 Series I. Governed by the MS standard series, administered by Military Standards.