Interesting Mavic rear derailleur from the early 90's.  Shared geometry with the Shimano Dura-Ace 7400 series making for a viable option to use early Dura-Ace STI shifters and a long cage derailleur combo!

This RD belongs to the Mavic Mountain Bike Group, also called "Paris-Gao-Dakar". Product Number (refers to Model) is 845. Most parts are similar to Road Model 842, except the long cage of course and some small parts.