Here is an interesting piece.
This Buffet Crampon A clarinet is a unibody, featuring full plateau keys with one "Donut" key.
The donut key was somewhat popular among Buffet products (see Buffet G Fischer and Buffet Antique Unibody pages) during the early 20th century.
However, this appears to date even earlier, from around 1860-1890, making this quite an early example of Boehm keywork.
Better yet, it features an articulated C#/G# key.
Cool!
OVERVIEW
Pitch: A
Key System: Boehm System, plateau keys, donut key, articulated C#/G#
Maker: Buffet
Brand Name: Buffet
Place of Manufacture: France
Approximate Date: 1860-1890
Body Material: Wood
Bore Type: standard, 14.7mm
Key Metal: Nickel silver
Keywork Quality: very good
Serial Number: 451N1
Recommended For: museum display or if you really need a plateau A
Value: up to $700