This is a new Kanstul M Series flugelhorn mouthpiece with French taper, in gold plate. 

Kanstul Musical Instruments was a pioneer in single-point scanning and mouthpiece duplication. Before the factory was shuttered, players from around the world trusted Kanstul for their accuracy in duplicating the most valuable and unique mouthpieces, as well as extremely consistent production mouthpieces. Among the hundreds of mouthpieces in the Kanstul catalog was the popular M Series, based on the Monette mouthpieces. This flugel mouthpiece is the M-4FL, a deep flugel cup for a rich, dark sound. Semi flat rim and a slight funnel shape as it meets the cup makes for a comfortable experience. If you are looking for a very dark and intimate sound, this is a very appropriate mouthpiece.

The mouthpiece shank is the French taper (which is sometimes referred to as the "straight" taper) and will only fit flugelhorn mouthpipes designed to accept a French taper. The French taper is an older, more traditional taper and may be more common in select geographic areas. The French taper isn't really a taper at all, but a 0.393″ (10 mm) diameter straight shank with a slight locking taper about an inch up the shank to securely lock the mouthpiece in the non-tapered receiver.

Popular vintage flugelhorns that will accept the French taper include Couesnon, Besson, and perhaps Mahillon. In recent years, contemporary horns that would accept the French taper include the Kanstul Model 925, and the Flip Oakes "Wild Thing" flugel.