Very tough question. I do know that in December only III./JG 54 and parts of JG 26 had already received the Dora, but it is definite that III./JG 54 did not fly operationally before December 27 (again, that is) and JG 26 was only in the process of receiving Doras throughout the month. JG 2 is known to have gotten Doras "in the days before christmas" as well, but being based east of Frankfurt/Main it's rather unlikely that one of theirs would head "north-east" from Liege.
