M. SAUR Clarinets?

[Windsong]

M. SAUR is not a name I have ever heard before, but perhaps the stamp was weak and this is just a partial Name/Cartouche.  The keywork is very odd, too.  The raised blocks for key mounting, the integrated thumb rest and the speudo-salt spoon keys point to a pre-1860 build.

I see a couple condition issues--the most significant being the missing key, but when have you seen another?   The price seems very good for what this is:

https://www.ebay.com/itm/397492365698?_skw=rare+clarinets&itmmeta=01KFE1VJ5CVAB5RBDVGTNEB0QY&hash=item5c8c642982:g:DeIAAeSwJOlpZsHI&itmprp=enc%3AAQALAAAA8KbGOR9kZR2XPHlEs4wKenOwsfYqsI50OEIk7YugaOVoJlFuOPswLw4hesELO4E79LgfCdno1Tk93Y2OsmqYQSC%2FcafyfRfVOA1bYWWaEXXCamoDJPM13kLowEuAC0g6LB9nok%2BJJojwYtpEM1%2FmuqaOkbTPYk7R3ry4ddyUhnZeanjNgjTSdUM3XKia8JDUM8KiodYqzVjJzW%2B5hQgJrrUnyDvnENEsGH2TdFaklrhcDmZ%2F6FhIjps56xhbUyurNiicT4dUnRKhNIafQ02c0lGr0zjKCqOtgYj%2BD104LighsmZbUdnedXbIS0xBiQiA7g%3D%3D%7Ctkp%3ABk9SR_Si7sH7Zg

[350 Rocket]

The stamping looks more like M.SAUB to me, although that doesn't seem to bring up anything either.

[Windsong]

I had the same thought.  I even tried a search with the last letter as a "K", which only enhanced my geography knowledge (Sauk is the name of towns in WA, MN, and WI). 

The closest name is Siour, (as in Siour Chapelain), and that's not it.  It's too expensive to purchase on a whim, but someone who knows what it is will want it for a museum collection or somesuch, I'll wager.