The 501-27510-81 from Wenzel Associates is a OCXO with Frequency 10 MHz, Supply Voltage 15 V, Phase Noise -145 dBm/Hz@100 Hz to -120 dBm/Hz@10 Hz, Phase Noise 1 kHz -160 dBm/Hz, Phase Noise 10 kHz -165 dBm/Hz. Tags: PCB Mount, OCXO. More details for 501-27510-81 can be seen below.