What is unique or rare about the VM Zodiac signs?

[MarcoP]

The crossbow in Sagittarius appears to be a topic of fairly high specificity, and it would be interesting to bring together a summation of current information. A list of relevant references - like the 'sleeves' investigation.

Possibly the google docs linked in You are not allowed to view links. Register or Login to view. might be a useful starting point. I am sorry that google somehow messes up the format: it might look better if you download it.
Yesterday I edited the doc to add Ellie's reference to the Pal Germ manuscript. I'll be happy to add any other pre-1500 crossbow Sagittarii that I might have missed.