There are three types of Zenith register hands.
Register hands that were original to the Zenith A386 are white with flat ends, with a hole at the center to attach to the wheel (you’ll see some replacement or painted hands that are solid white at the center). The hands can be either “thin” or “thick”, but regardless of type, all three register hands should be consistent in shape (not one or two of a different size/design), and all should extend to the end of the second/minute/hour marks. The thin hands were found on Mk 1 cases, and thick hands on both Mk 2 and Mk 3.
The third type of register hand we see has a pointed end. These pointed register hands are used for service replacements, although we also see them appear in the last of the Mk 3 production (231E1+) pieces. My working assumption is that Zenith ran out of the original thick hands and began to use these pointed service hands on the final few hundred pieces of production, as I find it difficult to believe this type of design change would be intended at the tail end of production, even more so with no other changes made. Hopefully marketing material or advertisements will be found from this period in order to more conclusively say.
As an aside, when there are possibilities as to what is “original” to a watch, I generally take the conservative route and purchase those with all components commonly accepted as original to the watch, which can make it easier to sell if needed.
Within the hands for each of the registers, the running second and minute register hands are the same length, with the hour register hand slightly smaller, though again same in shape:
Just judging by photos, I am estimating the hand length of the seconds and minute registers at 5.0mm and the hour at 4.2mm for a Mk 1 (539Dxxx).