Du Mont RA112-A3 and color?

[Penthode]

I just acquired a Du Mont RA112-A3. It is a late run chassis according to the Rider's service manual which puts it manufacture probably at the end on 1950.

I noticed on the back cover "Video Out to Color Converter". The video output is via an RCA connector and this connection is not shown in the diagram from Riders Volume 6. Nor in Riders is the DPDT switch next to the connector which is not marked. (A standards switch?) I have yet to follow where the video is extracted but I expect it is somehere from the video amplifier stage. And as for the mystery switch, I will have to trace this out as well.

This is interesting since the late 1950 coincides with the FCC acceptance of the CBS color system. My guess is that perhaps the switch alters the horizontal and vertical time bases and the video out may be to provide sync for an external sequential filter device? If a separate color wheel was considered for this set, it would have to be a monster diameter: the tube is a 19AP4 and therefore the disc would have to be about 40" in diameter!

(It make me chuckle to think how hazardous television servicing could be in those days: HV on metal cone CRTs and huge spinning discs could lead to horrendous accidents!)

Has anyone else seen such connectors and switches on 1950-51 vintage TVs?