Help with identifying some mystery rifles and mods (pics inside)!

[vigilandy]

I spotted some nice looking airguns on gunbroker and proceeded to contact the seller.   In the course of discussing the purchase of a gun, I found that the seller had acquired the collection of an airgun enthusiast.  The seller isn't too familiar with air guns, and I'm not much help, so I offered to post some of the pictures on the forum. 

FYI, I don't know the seller personally, but he has good feedback, and also told me the name of the person who owned the collection.  I have no reason to suspect any foul play.  And if it's not clear, I don't have any connection with the seller other than being a customer.

So here we are.  Let's play a game of "can you spot that mod?"