Consider this complete Reference Standard with Interface Board + Heatsink + PSU.
The SRS PRS10 rubidium oscillator 10 MHz reference standard has an extensive command set to monitor and control it using a terminal emulator or the RbMon application. It is more sophisticated than the Symmetricom SA.22c or Efratom LPRO-101, two other available reference standards.
You can upgrade performance with an SCSKITS interface and disciplining the oscillator with a Leo Bodnar LB-1421 GPS locked clock source.
Quick bench test results (will update listing with pending long-term test):
- Allan Deviation (ADEV 4000s = 8.29E-12) measures frequency stability by analyzing phase fluctuations. This unit deviates 8.29 parts per trillion (±82.9 µHz) over 4000 seconds and may be further improved through GPS discipline.
Serial number 12320. The PRS10 is still in production and sells new for $1,895.
Performance of a rubidium standard deteriorates after decades, and many on eBay are over twenty years old. While an older unit may still be performant, you cannot tell unless its stability is verified.