YEP-321

This euphonium is still manufactured to this day without any major design changes since it first went on sale.
There is something with that degree of design perfection that deserves special mention -- the B♭ horn. Featuring a four-piston valve system and a 280 mm-diameter yellow brass bell with bore size of 14.5 mm (1-3)/15.5 mm (4), and finished with a clear lacquer.