I agree with ir3333. I opened a PDF copy of the 69 Service Manual, and it shows that location as either being a convertible top control or a fader control for the front and rear speakers. And since you probably don't have a rag top, there you go.
The convertible top control and rear defogger control share the same location since you can never have both options on the same car. That location is to the left of the steering column. So, I think the one in the picture is a fader control.