I recently received five Rakon VTX0225AR 10 MHz VCTCXO's. While I did not need GPSDO precision, these came closer to that than I expected--0.05 Hz drift during a recent 3.5 hour test. See the first attachment.
The second attachment shows the oscillator board with its metal cover removed and terminals labeled. Another picture floating around has those terminals incorrectly labeled. Besides having a trimmer capacitor available for adjustment of its frequency, it has a control voltage terminal where the frequency can be more finely tuned. That is how I adjusted the frequency to that shown on the first attachment. Even with the trimmer capacitor set for the highest frequency possible, it seems like most or all of the units do not quite make it to exactly 10 MHz. However, it is obviously possible after adding the voltage adjustment. Accordingly, that voltage adjustment only seems to raise the frequency. Via a fixed and trimmer resistor combination, I have the electronic frequency adjustment range set to 10 MHz +/-10 Hz. That makes fine adjustment easy via a 25 turn trimmer.
The VTX0225AR has a clipped sine wave output. Attachments show that on my oscilloscope and spectrum analyzer. While ALL harmonics only go down slightly at higher frequencies, I saw almost nothing in the way of modulation products or IMD very close to its 10 MHz frequency. While it is possible to add a bandpass filter for using one of those harmonic frequencies, the last two attachments show its output with a Mini-Circuits SCLF-10 10 MHz low pass filter connected to the oscillator's output.
What do these things cost? How about $2 each? A quantity of five is available on eBay for $10. See:
https://www.ebay.com/itm/232248869943 That auction confuses things by highlighting the oscillator's reel number rather than its part number shown in the pictures.
So far I am very happy with the purchase.