The part number is CAP CER 91PF 50V C0G/NP0 0603. It represents a ceramic capacitor with specific characteristics: a capacitance value of 91 pF and a tolerance of ±2 percent, along with a voltage rating of 50 volts. The capacitor adheres to the C0G and NP0 specifications, indicating its stability across temperature changes. Its dimensions are in accordance with the 0603 (1608 metric) package size.