[Drake] mixers in the R4C

[Joseph Trombino Jr]

Howdy Drakesters:

Is there a serial number cutoff for the R4C variations that used the 6EJ7 or 
6HS6 mixer tubes???

I have a high serial number (28K) R4C coming in and am wondering about the 
mixer type so that I can find the correct manual for the radio.

Basically, what mixer tube was used in the later R4C's (0ver 25K s/n).

                                    73, Joe W2KJ
                                    Soon to have a C-line on the air