I am forwarding you a method to do the calibration of the 4 Mhz master oscillator of your K2 using RWM on 9996.00 Khz.
After a nice exchange and advice from Don, W3FPR, please find enclosed the way I used to set the 4MHz oscillator. It really works FB!!
The only you will need is to download Spectrogram (if you do not have it already). This software is really helpful to zerobeat the carrier. You must just prepare a cable and connector to feed the audio signal picked up from the speaker output to the line or mike input of your sound card. So, the procedure is as follows.
Please note that RWM transmits an unmodulated carrier during 7 minutes after the hour and after the hour and half.

1.- Start Spectrogram and set a marker corresponding to the frequency of your ST P (you can check that the marker is OK with the spot function).
2.- Select LSB and tune RWM. You must zerobeat the carrier.
3.- To check that the carrier has been correctly zerobeated you must switch to CW and realise that the tone corresponds to the marker of your ST P.
4.- If the tone is not on top of the marker you can re-tune until it is (you can then switch on SPOT to realise the beating between the carrier tone and the K2 ST).
5.- Without moving the encoder, go back to LSB.
6.- Now you must follow N6KR method. Run CAL FCTR and move the frequency probe between TP1 and TP2. At this point you must adjust C22 until the less significant digits are the same this will mean that the difference TP2-TP1=9996.00.
Please note that the TP1 will change about 5 times quicker than TP2, so be careful with C22 adjustment. You will immediately realise if you are adjusting right or not because the difference between TP1 and TP2 either will increase or decrease.
7.- Once C22 has been adjusted according to point 6 you must witch to 40m connect the frequency probe to TP1 and run CAL PLL
8.- Last but not least you must run as well CAL FIL for all the filters and modes.
9.- You can check now that the dial  of your K2 is well calibrated tuning again RWM and realising that the frequency shift is between +/-10 Hz. If it is not you can iterate going back to point 2.

I have done the calibration of the last K2 I built using above method and it has worked very well.
Please note tha Spectrogram is just used to check for the right zerobeat of the carrier. It is impossible, at least for me, to detect an audio tone of 0 Hz, while switching to CW tells you with a reasonable accuracy that you tuned RWM correctly.

VERY IMPORTANT!!. Do not forget to switch to LSB before adjusting C22 (steps 5 and 6). If you do not so you will add the CW offset.

This method is just a light refinement of another method described by Glen Worstell, KG0T, but the main advantage is that it is independent of the ST P because it uses the programmed shift between LSB and CW which allows to check that the carrier has been correctly zerobeated with the help of Spectrogram (useful visual aid at least for me).

Please feel free to contact me whenever you may have any additional questions or comments.

Best 72

Vicenç Llario, EA3ADV