The reason in the Simp is probably that you have just one common and several inputs for AC and DC voltages, ohms etcetera. The common is a good place for a fuse.
It does not give you any problems with high potential on the GND because it is a closed instrument and GND is not possible to touch.
Also, this is 1950 technology and no one cared back then. The more problematic fact is that the test leads are non standard and that it is not possible to connect safety-enhanced test leads. But, who cares? You can have instruments superior to the 260 for something like 20 bucks. And real safe and high-quality instruments for around 100 dollars.
Those old instruments sure used to show you the action of the circuit under external loading.
When was the last time any of us had to use the Ohms per Volt rating to determine the circuit loading that the test instrument would present?
Was the Simpson one of those with quite a low Ohms per Volt or am I confusing it with another old "quality" name?
And for a really low Ohms per Volt, does any one remember the Wigginton (Wiggy) voltage tester. The older the lower!
Bill
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"Why not the best?"
Jimmy Carter
The old Wigginton Voltage testers used a solenoid coil pulling an indicator down a scale. You could tell AC from DC by the lack of vibration on DC. I never measured the Ohms per Volt but we used to joke that they would dim the lights. Over the decades they became more refined and more sensitive until the moving parts were replaced by a line of neon indicators. One model that was around for a long time had a pivoted magnet inside a clear plastic cap on the end. It would align with the magnetic fied of the solenoid and indicate the polarity of DC.
They were crude but rugged and dependable. I imagine they saved many lives over the generations that they were in common use.
Bill
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"Why not the best?"
Jimmy Carter
I wouldn't give much for a 260 even though I sold one on ebay not too long ago for $120. Guess some just want to live in simpler times. It is common to put a higher amperage fuse in series in the event someone replaces the easier to get at lower current fuse with something much higher than it should be. I've replaced a number of fuses with gum wrappers and pieces of wire when I was in a pinch. Many older audio amplifiers did the same thing. Can't tell you how many 20A car fuses I saw in equipment brought in for repair in my college days!
The Wiggy testers were great, they put a load on the circuit so you wernt fooled by the capacitive coupling between wires which could easily fool a high impedance meter. An AC multimeter will not read when it's applied to DC (or have I got that backwards) wheras the Wiggy would always warn you.
Roy
It was the interrupting current rating.
It turns out the 2A was protecting the equipment and the 1A was protecting
the (presumably more costly) 2A from nuisance tripping.
Even in the dark, you could feel the vibration on AC and one pulse on DC.
Another big advantage over multi-meters was couldn't check voltage with the meter inadvertently on Ohms or milli-amps. I never had a multi-meter blow up in my hands but I have heard descriptions of large power breakers (1400 amps) being tripped by a multi-meter. Sure glad it wasn't me holding the meter.
As you mentioned, some multi-meters use a capacitor in the AC circuit to block DC.
Bill
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"Why not the best?"
Jimmy Carter
