Mystery Martin Freres Supra Clarinet

Having a home based business in a small town is occasionally interesting: yesterday morning I heard the doorbell ring, and saw a woman with a clarinet case. This is not a completely uncommon occurrence (although I generally get a phone call first, so I'm not just standing there in sweatpants, as I was yesterday) but she wasn't here for a repair estimate - she wanted to give me the clarinet! 
 She told me that she was moving to Colorado and wanted to lighten the load before she departed. Now, on the rare occasions that people want to give me clarinets for free, they tend to be worth what I'm paying, so I wasn't too optimistic. However, I opened the case and found this Martin Freres Supra...

Now, of course I've heard of Martin Freres (an old and somewhat obscure French maker, generally known in later days for undistinguished student instruments), but I've never seen anything like this! Seven rings, extra key-cup on Low F for intonation, silver-plated keys and rings, post lock-downs, factory tenon rings....it gives every appearance of a really nice professional quality horn. So, I'm curious: does anyone have experience with one of these or know anything about it? I'm going to start tearing it down for overhaul today, and would love to hear your thoughts....