Ampeg V4B. Nearly identical to V4 but has an Ultra Lo switch for extra bass and no reverb. Also missing the sensitivity switches for Vol 1 and Vol 2. Recapped by someone else and pretty nicely maintained. Clean too. There is a big good write up on V4/V4B on the Electronic States site that says more than I would ever write, check it. I see these a lot with cracked solder connections on the preamp tube sockets. I’m not 100% sure why this is, but I would guess it has to do with the large range of heating and cooling cycle these amps go through since they typically run hot, with tubes hanging under the chassis, lots of power, lots of tubes, big transformers, etc. Back in the day when I used to run my V4 with 6550s and break it all the time the front panel would sometimes be almost too hot to touch after a 2 hour practice. That was fun back then.
Maybe the tone secret to the V4 is that almost all of them have the silkscreen wore off the front panel which makes the musician actually have to dial in a good sound by ear. Actually I guess there could be varying results with that.
Ampeg V4B schematic