The Spectracom 8163 is a WWV Receiver plug-in for the TM500 system. It produces a frequency of 0.1, 1, 5 or 10 MHz locked to the WWV-transmitted reference frequency.
According to Spectracom's Retired Products page:
WWVB referenced frequency receiver. Will no longer operate as intended due to the changes in the WWVB signal in 2012.