i have a Drawmer M-Clock, one of the 1st made by the factory, very low serial = old.
has dual TCXO, like all decent analog hybrid clocks, like Grimm Audio CC1, etc...
single quartz oscillator clocks are usually DDS or PLL "inferior", unless it has 64-Bit DDS controlled by a OCXO with Rubidium 10MHz option, like Antelope Trinity.
Aging usually is done at the Quartz cristal oscillator factory "burn-in", because it seems that drifts the 1st days very fast.
Urban Legend style...
the TCXO i have, can be calibrated with a small plastic screw driver, each, moves/tunes the capacitance of the circuit feeding the quartz oscillator.
increasing or decreasing the oscillating frequency in very small amounts...
i have an Oscilloscope with Real High Quality Frequency counter, most Digital Oscilloscopes are Software counters "crap/useless", like Keysight, Pico scopes, etc...
i can calibrate the TCXO to be exactly 44.1 x512 & 48khz x512 =
22,579200 MHz
24,576000 MHz..
some clocks are x256 other x512, other x1024, internally,
but the wordclock output signal is 192KHz max,
AES/EBU or S/PDIF black / empty signal is 6MHz aprox.
https://groupdiy.com/index.php?topic=61952.msg791132#msg791132
because the internal clock division, the real wordclock output frequency is:
44.1000 KHz,
48.0000 KHz,
88.2000 KHz,
96.0000 KHZ +/-1~2 ej: 96.0002 ~ 95.9998
176.4000 KHz +/-1~2
192.0000 KHZ +/-1~2
thats called 1ppm "1 part per million drift."
Drift is different than jitter, i recommend you read the Grimm Audio white papers in .pdf to learn more about that.
for example:
a +-/1ppm clock drift will have perfect pitch over 200Hz,
but jitter is different, related to Phase Noise, but Not the same...
Grimm Audio has the lowest Phase Noise design ive seen.
Apogee Big Ben has lower RMS than Mutec iClock, but iClock has less/smaller peaks.
there are 3rd harmonic Resonant clocks design like Black Lion Audio mk2,
they create the frequency needed, indirectly, as a harmonic of other, and eliminating the fundamental frequency.
Analog Digital Hybrid, "dual Quartz, HCMOS circuit or Dual TX with Digital circuit like Rosendahl Nanoclocks.", better designs can be Temperature Controlled / compensated.
http://studiorepair.com/gallery/misc/Rosendahl_Nanoclocks/slides/Rosendahl_Nanoclocks_Circuitry__STUDIOREPAIR_10101801_1210302530.html
DDS "Direct Digital Synthesis" limited by Negative feedback and Bits of resolution... the best is Keysight TrueForm DDS generator, Similar Apogee Big Ben, mutec iclock, Antelope, and others...
3rd Harmonic overtone like BLA Mk2
1x Quartz, silicon PLL type. "usually cheap, included in low cost equipment like Focusrite 18i20 mk2"
VCXO, tuning frequency is controlled by voltage ..
are some of the types of oscillators "XO",...