[Big John]

Those are designed to be used for current carrying conductors, the style in the OP's pics are not.

You sure? I don't use those because I don't like them, but looking at Ideal's website, these are the 2006S crimps:

And these insulators are designed for 2006S or 2008S:

Though I agree in OPs picture it definitely appears to have been used improperly (wrong crimp tool and no insulator), I think they could've been used safely.

 

[Big John]

Bah. Done right there's no reason it shouldn't have lasted for 70 years. It doesn't do anything but sit there.

 

[Big John]

I don't believe that for one minute. Receptacles and switches in rental properties see some SERIOUS use....

What I see there doesn't look like the result of device failure to me. I could be wrong, but it looks like conductor faults. No good reason for that to happen.