This 90 yr old house of over 2000 sq ft still uses the old fuse panel for most circuits. Service was upgraded a bit to 100 Amps, but that was so they could install a plenum-type heater, that needs a 100 amp supply.
They installed a Federal Stab-Lok panel with a max rating of 125 Amp. The 60 amp breaker on the right supplies the old fuse panel, the one on the left is 100 a for the furnace.
Then the oil-fired water heater failed, so they installed a third panel, another Stab-Lok, on two 20 Amp fuses.
The square ammeters in the first panel are for a second meter which records power consumption for discount prices, not transferrable to the new owner.
My client now wants to sell. Too bad this whole mess was a waste of $$ and did nothing to raise the value of his property.