Silverface Bassman 50 from 1974 I believe. Same era amp as the Twin Reverb in the previous post. This amp has a slightly different phase inverter design compared to the earlier era Bassmans.
There are a few other variations I’m sure but I’m not all that familiar with them, era to era.
Chassis image and amp is all original and still works, just needs new power tubes. Recap could be nice for possible reliability but customer decided to let the good times roll.
The trimpot more easily visible is a balance adjust to balance current draw for the two power tubes. A bias trimpot was installed right next to it to dial in the new tubes. The 470 ohm screen grid resistors measured about 510 ohms and 890 ohms and were replaced. No longer original oh well. At least it works better now.
Fender Bassman 50 schematic