What is unique or rare about the VM Zodiac signs?

[ReneZ]

One has to be very careful with the terms "astrology" and "astronomy", because the modern distinction does not apply to these times. (Marco already pointed it out too).
The reason why the ancients were interested in the stars was more like what we would now consider "astrology", and it wasn't nearly as "esoteric" as modern astrology is.
The text below the illustration, talking about two stars, refers to the illustration on the next page, and their "image" is that of two women.

In modern terminology, this MS leans more towards astrology, describing "images" of stars. The "image" of the two scorpions (with their specific details) belongs to the single star that is now known as Antares.

All of this would have been hardly possible to find out from the WWW in 1998, and once the wayback machine is back up and running, one can see just how little was visible then.

My original point, that I remember seeing an illustration of two lobsters for cancer, still remains open....