To add on, the "Maestro" name was what Yamaha called the 642 euphoniums sold in the UK/Europe. Other than the added name, they're exactly the same as the older 642s you might find used for sale in the US/Japan, for example. There's a newer version of the instrument called the 642II "Neo."
Willson 2900 TA-1 Euphonium - Denis Wick 4AM
Yamaha YSL-643 Trombone - Bob Reeves BrassArk 5G "Gladstone"
Yamaha YSL-8440 Trombone - Denis Wick 5BS
VMI 3301S BBb Tuba - Schilke Helleberg
Past:
York Preference 3067 Euphonium - Denis Wick 4AL
Benge 165F Trombone - Benge Marcellus
Wessex BR140 Baritone - Denis Wick 6BS
F.E. Olds Special Trombone (ca. 1941)