The 501-17998a from Quantic Wenzel (Wenzel Associates, Inc.) is a OCXO with Frequency 5 - 100 MHz, Supply Voltage 15 V, Phase Noise -135 dBm/Hz@100 Hz to -120 dBm/Hz@10 Hz, Phase Noise 1 kHz -155 dBm/Hz, Phase Noise 10 kHz -174 dBm/Hz. Tags: Module with Connectors, Thru-Hole. More details for 501-17998a can be seen below.