Distinguished SOTW Technician
10M's are the fastest tenors on the planet--it's to do with the key cup to hinge leverage. If you look closely you will notice how the key arms actually follow the contour radius of the body tube. Most other horns feel like typewriters in comparison. Combined with long springs and the (in)famous locking pivot screws the keywork can be set up like 'greased lightening' 6M's work on the same principle. I've often wondered if the extra keywork and adjustments to be found on Conquerer's (26m ,30m) slowed the action down somewhat compared with their 'lesser brethren' so few people bought them--to the point they were discontinued.