Unknown rear Suspension

Hey,
I recently bought two yamaha XS850SG's for the purpose of fixing and selling them to fund the KZ addiction, and on the parts bike the rear suspension appears to be an aftermarket air ride deal. I was wondering if anyone knows where these came from or how much they are worth. They seem to work fine, as in hold air, but the labels are a little sun bleached and the chrome is starting to rust over. It says MS Mark II, and thats all I could find. Any ideas are appreciated. Thanks,
-Jared

They look like SW shocks, decent for their day. As far as value...well thats open to debate but think about this they are old shocks and unless they are old race shocks that are rebuildable would you pay lots of money for them?