above: Completed Yamaha YBB-641 Tuba, ca.1977
Before photos on the left:
The after picture above shows an installed #4 lever. This particular Yamaha Tuba is a 3 digit serial number which makes production between the late 1970s to the mid 1980s. The original #4 lever is obsolete. Luckily for me, I had all of the other parts; stop arm, linkage and various screws. I retrofit a modern YBB-641 lever using a french horn linkage ball socket to connect the new lever to the old style linkage.