So, the three traces are all for the same oscillator? Green - 1 day ago, Pink - 4 weeks ago, Blue - 6 weeks ago? And that oscillator has been powered up almost continuously over that period?
The green trace has higher noise levels than the others. That's why it's been pushed up. Notice that at the 1 second point, it's at ~9e-10 whereas the other traces are ~6e-10. The lack of ripples in that graph may or may not be significant. It could be that the noise is masking the ripples.
The part of the green trace from 200 seconds up looks quite good. A flat section like that shows the noise floor of the measurement. There is no hint of aging like there is in the red and blue graphs. But again, it might be that the noise is masking the aging.
I don't know what else to tell you. If you want to buy some more oscillators to compare with what you've got, go for it.
Some good brands of quartz oscillators are Wenzel, HP, Symmetricom, Oscilloquartz, and MTI. There are others - that's just off the top of my head. Stick to 10 or 5 MHz unless you have a reason to get something different. Newer units have the benefit of better technology, but older ones have the benefit of time to stabilize. The longer an oscillator runs, the better it gets. An old, high quality oscillator can be a magical thing - or a paperweight.
![Banging Head |O](https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gif)
Make sure that you get ones that have EFC - some don't.
Rubidium oscillators on ebay have gotten expensive in the last few years and it's hard to tell the difference in specs between things like the LPRO, FE-5650/5680, or X72 so there's not much point in stocking up on them.
Ed