Calling all wheel/tire experts!

For some reason, my RS has what I think are early early 6" wheels on the front. I'm not an expert on the early vintages, but I assume that these are what're referred to as "deep" 6s, since the 5 spokes have a pronounced curve inward at their OD, making for a deep groove just inside the outer rim. They definitely look different from the 6s with which I'm more familiar, that are basically flat between the outer part of the spoke and the rim. My questions are:

1) Am I correct that these are the early wheels referred to as "deep"?

2) What was the last year that these were used in production?

3) Is there any possibility that Porsche would have put them on a car as late as '73?

4) I've been told they are meant to be used with tubes - any fundament issues with using them with tubeless tires?

5) Are these wheels worth more or less than the later 911 6X15?

Thanks for the help,
Lee