The 'Kanstul' marking on your trumpet dates to, at the earliest, 1981, when Zigmant Kanstul launched Kanstul Musical Instruments in Anaheim, California. One poster to a brass forum mentioned that his Besson Brevete (often spelled?Brevette?) was made in the early 1980s, and mentioned a 4XXX serial number, comparable to yours. All existing Kanstul French Besson trumpets have 3, 4 or 5 digit serial numbers (got to about 7,000 by 1998, now at around 40,000). Many non-Kanstul.

The Martin Companies
Frank Holton and Co.
Vincent Bach
Plant changes at Bach - 2017
Col. C.G. Conn & Co.
Harry Pedler Companies
Boston Musical Instrument Co.
Bohland&Fuchs stencils
Sistek Music and Cleveland
Ross Hickernell
F. Millard Company
Willard Bryant - Rex*
O.F. Berdan - Detroit
Connections Among Makers
Getzen History Chart
Fred Forman's cornet
Cold War Collectives
HN White - first for students
HN White's first cornet product
Study - Instrumental Inheritance (pdf)
Evolution of the Modern Trumpet (pdf)
Drum & Bugle Corps Origins
Birmingham [Mi] Bands (pdf)

Besson Loyalist

Kanstul Trumpet For Sale

Kanstul Besson Brevete Trumpet Serial Numbers

H.N. White Co's History of the Trumpet and Cornet (1924)
Jim Donaldson's biography of Renold Schilke at EverythingTrumpet.com
Niles Eldredge's Brief History of Piston Valved Cornets at Nick DeCarlis' VintageCornets.Com
Dale Olson's History of F.E. Olds at Robb Stewart's site
CG Conn History articles at the Conn Loyalist
Contempora Corner histories of F.A. Reynolds
Chris Charvat's HN White History
Woodwind & Brass Co (Britain) history of Antoine Cortois
Mitruolia/Myers The Distin Family
Robb Stewart's biography of Earl Williams
Jari Villenueva's History of Taps