Agree with larry, likely is 120 volt supply, from the top left cable. Look carefully the black conductor goes to top left terminal of disconnect. White disappears on us but pretty sure is the one landing on left ammeter lead, then right ammeter lead lands on the top right terminal of disconnect. Lots of old installations had fuse in both lines, some may not even been grounded originally and maybe part of reason why fuse in both lines. They are metering the white supply lead (whether it is grounded or not).