Holton "Jumbo" Trumpet
You might be saying "This guy is more clueless that I realized" for calling this "Jumbo" rather than "MF Firebird", but I really do know that story behind this unusual trumpet. "Jumbo" was a nickname of Al Hirt, who was at the height of fame in the 1960s, when Leblanc Corporation introduced their Al Hirt model trumpet. This was made in Paris by the Courtois branch of the company and marketed under the Leblanc brand.
By the early 1970s, a US made Al Hirt model trumpet was introduced by Holton, another branch of Leblanc. Also, about that time, Holton's chief designer, Larry Ramirez, came up with a trumpet design that he thought would be ideal for playing jazz, because it has the normal three valves and also a slide with about 4 positions. This allows the player to employ trombone like glissandi, smears and bends as well as adding a few notes in the low register. The first prototype was retained by the factory and this second instrument was engraved with the nick name and sent to Al Hirt in New Orleans. He didn't use it much, finding his more standard Holton trumpet satisfactory for expressing his musical ideas.
Holton then offered one to Maynard Ferguson, who really liked it and used it often, to great effect and fame. At this time the model was named “MF Firebird”. A decade or so later, Hirt had a very talented young trumpet player in his band named Larry Lunetta. Larry was curious about this odd trumpet and with Hirt's encouragement, picked it up and played some improvisations on it including the slide. Hirt said that he had never seen anybody play it so well and gave it to him on the spot. Larry kept it for another 15 years or so, but eventually decided to part with it, offering it to me. It's difficult to put a value on such an instrument, but we made a deal that made us both happy.