Nothing else is special. It can pull considerablly more frequencies than the conventional one. About 40kHz for a pair of 10.15MHz X-tals, and 90kHz for 13MHz, according to my experiences. The followings are my experimental results. I built a 30m direct conversion QRP XCVR with it.
Frequency is very stable.
The transistor used is again 2SC1815. This coil is slug-tunable with a core of small temperature coefficient. This Super VXO is used in my 6m QRP SSB super-het XCVR . Frequency is acceptablly stable but not so stable as the above example of 10.15MHz. I have results also on 20m CW XCVR and 40m CW XCVR .