We can not judge.
The quality will be judged based on the actual product check.
Silver oxidizes in the air and becomes oxidized silver.
And silver also sulfurizes by sulfur that is contained in corrugated carton.
As the results, the color becomes black.
In case the oxidization layer is thin,  it is removed by insertion/withdrawal and
there is no problem on the conductive performance . 
Please keep silver plated products in sealed conditions with a desiccant (drying agent).