Over the years I have seen three or four later followers with the early slide. Always loose in parts bins, never on a rifle. Other than that, I know nothing else about these anomalies.

I always assumed these followers were put together after the fact.
Thought about purchasing one for curiosity sake but never did. And the days of the voluminous parts bins at shows are long gone around here.

I remember at least one follower had a straight back slide as seen in the ebay offering and at least one had a 45 degree slide as shown by RCS.

These observations were years ago and the asking prices were nowhere near the amount the follower on ebay sold for.