The 501-27228b-04 from Quantic Wenzel (Wenzel Associates, Inc.) is a OCXO with Frequency 50 MHz, Supply Voltage 12 V, Phase Noise -135 dBm/Hz@100 Hz to -104 dBm/Hz@10 Hz, Phase Noise 1 kHz -156 dBm/Hz, Phase Noise 10 kHz -170 dBm/Hz. Tags: PCB Mount. More details for 501-27228b-04 can be seen below.