[unruhjonny]

I will start out with this;
The multiple different reproductions out there - with various quality levels sure do not help matters.

I have all four versions of the three speed knobs used in second gen cars, as well as some of the four speed stuff.

The "raised aluminum insert" was actually am aluminum part which was painted, and had a layer of epoxy(?) set on top.
I have a couple used aluminum four speed inserts that are missing the epoxy top (which presumably took the paint with it.
I have personally handled many of the aluminum insert four speed knobs, but do not own one.

First:
It appears that when the black oversized round ball knobs were phased out, the leather knobs were phased in;
My opinion (not founded in any hard facts, mostly conjecture) is that four speeds were built in higher numbers than three speeds;
Because of the difference in build numbers you will see change over at different times - and presumably less orders needed to be filled out for GM on three speed parts.

I believe that the black ball was used in three speed cars through to 1973, while it was phased out on four speed cars in 1971;
It is worth noting that (my understanding is that) the same oversized black ball was used on the A-bodies through 1973 regaurdless of transmission.

Second:
I believe that the raised insert on the aluminum base was in essence an update on the insert used prior to 1970 with the wood knobs;
This is why the "early 1970" simulated leather knobs had the same red inserts used on the earlier wood knobs.
The updated insert was the same construction, but a different design on a "new" handle.

I believe that the raised insert (on an aluminum base) was phased out for the 1977 model year.

Third:
I believe that during the production run there were two running changes that may have created an unintended extra variant as far as purist restorers are concerned;
1) cheaper insert/emblem
2) revised handle to set insert/emblem flush

Summary:
Four speed:
1971.5 through 1976.5 = raised insert on aluminum base
1976.5-1978(?) = slightly raised insert; insert is 100% acrylic(?) with simulated silver edge
1979-1981 = flush insert; 100% acrylic with simulated silver edge

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Where the three speed and four speed knobs differed is the raised/aluminum insert was never used with the three speed - other than the pre-production/early production 1970 cars;
This means the three speed design shown in prior posts has never (to my knowledge) been found on an aluminum base;
Instead, when the black ball was phased out for the three speed handle, PMD immediately swapped to an insert with a black plastic base more akin to what was used on period key fobs (keep in mind three speeds were rarely an option, so keeping all components cheap would have been a priority).
I believe that a simulated leather or wood knob was generally as far as a dealership parts department, and was often ordered.

Three speed:
1970 through 1973(?) = black ball
1973(?) through 1978(?) = raised insert on black base
1979-1981 = flush insert; 100% acrylic

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The worst offender in my opinion of the four speed reproduction knobs is the one which uses an insert that is like what older key fobs used - and this "sticker" is set into the recess on the knob... they just look awful.