What d'you mean, "what now?", you wanted to know how old it is, I've just told you, it's a version 5 op-amp Muff with pots dated from late 1979.
as for volume, my Big Muff, which is the same model, boosts my amp with the volume at about 10 o'clock, so if yours is really quiet there's definitely something wrong. Check all your solder connections, check every component with a multimeter against a schematic, and clean the pots with some Servisol or similar electronics lubricant.
This is the most accurate schematic I've managed to find:
