Penzel-Mueller Pruefer

The eBay add for this said
LP Bb advanced Boehm system Uni-Body clarinet. Uniquely, the instrument is branded with both Penzel-Mueller and Pruefer, the two most significant American clarinet manufacturers of the age -- note, however, that the brand names appear together on the logo (i.e., this is not a "hybrid" or "frankenhorn"), which makes the horn something of a rarity. Dates to c. 1925 and is grenadilla wood with nickel silver keys and a bore of .580".
This sold for $650, by the way.