I have 9 Temex Rb MCFRS-1, of which 4 are good and 5 are bad. These oscollators could be ordered with up to 4x10E-11 / per month drift. The best one I have (serial number 1265) could fortunately be one of these.
Some interesting documents and Adev, from the best I have (SN: 1265), against a Samsung UCCM-L8 GPSDO.