The 501-27555-81 from Quantic Wenzel (Wenzel Associates, Inc.) is a OCXO with Frequency 100 MHz, Supply Voltage 15 V, Tuning Voltage 0 to 10 V, Output Power 13 dBm, Output Load 50 Ohms. Tags: Module with Connectors, Low G-Sensitivity. More details for 501-27555-81 can be seen below.