You are not going to get flamed by me, dont beleive in it
That is the 'classic' DT830. I have one that is 15 years old, the rotary dial is a bit dodgy now.
I am surprised it survived mains on the ohms range, they normally die.
Can you do some pics of the insides please?
Yes, they can be pretty accurate, at least to sepcification.
After all, they are based on a really simple, rock solid, dual slope ADC.
They are as good as the resistors that make up the resistor dividers.
I would not say it is safe for mains work, watch mjlorton video when he visited the fluke lab to see how badly they can blow under the right circumstances