The 501-27513-33 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 -105 dBm/Hz@10 Hz, Phase Noise 1 kHz -158 dBm/Hz, Phase Noise 10 kHz -167 dBm/Hz. Tags: Module with Connectors, Thru-Hole. More details for 501-27513-33 can be seen below.