The answer may be difficult to pin down due to various time periods where procedures and suppliers may have changed as well as ownership as with CBS's involvement.
And when we add in changes to the drums over the years performed by their owners, it can be difficult to know what is correct. The key is the drums that were barely used and stayed with their original owners for decades. I just saw a post today about a 70's Slingerland kit that fits that criteria where the owner bought them new, tapped on them a bit and then packed them away. Those sets are almost priceless when found. Jollity Farm had a Red glitter Rogers set like that many years ago, but it was the parents who bought it for their child but after hearing them, packed away the drums.
MY interests since the mid-60's have been both drums and Ford Mustangs, and my involvement with related forums such as VDF has swung both ways according to my current level of interest. Until recently, I was heavy into the Mustang forums and little with drums. I sold what I am considering to be my last Mustang a few years ago so I started to re-enter the world of drums as a pass time. I believe I am starting to notice similarities in the two hobby's interests of both drums and cars when it comes to originality.
Just with Dan's topic and question on the configuration of tension rods as was supplied on the drums when new, the same questions surfaced on the Mustangs. If I am correct in that there was only one factory manufacturing each brand of drum, it would simplify the process of determining what was done during certain time periods. With the cars, there were extra variables besides the typical, such as multiple manufacturing plants that acted as independent units that did their own parts requisitions and building techniques where developed separately from line experience in addition to engineering design changes. With multiple plants, the variables increase practically exponentially, even the work shifts ( 1st, 2nd, 3rd, P.T. & W.E.) and the workers themselves caused cars not to be the same.
When the cars were new, I didn't concern myself with what was factory original. But with ensuing years when restorations became necessary, the pursuit of originality became utmost especially for the purists. I was fortunate that the 1968 Mustang I sold a few years ago was almost all original with 11,000 miles on it, whereby the tires and battery were the main parts that were not. Since it remained untouched, the factory processes were blaringly evident, even to the extent that the differences in line a worker's 'touch' was detectable. For example, there is a difference between the left and right rocker panels in the manner which they were painted since there would have been a worker on both sides of the car working independently at different stages of the build.
Sorry for the rambling and off topic wandering, a bit of reminiscing and a touch of regret mixed in there too.